Selecting JARVIS in the OPTIMADE client raises an error

**Describe the bug**

When trying to use the JARVIS database for selecting a structure, the app crashes with the following error:

Full Traceback

---------------------------------------------------------------------------

StopIteration                             Traceback (most recent call last)

/opt/conda/lib/python3.7/site-packages/ipywidgets/widgets/widget_selection.py in findvalue(array, value, compare)

    136     try:

--> 137         return next(x for x in array if compare(x, value))

    138     except StopIteration:


StopIteration: 

During handling of the above exception, another exception occurred:

ValueError                                Traceback (most recent call last)

/opt/conda/lib/python3.7/site-packages/ipywidgets/widgets/widget_selection.py in _validate_value(self, proposal)

    240         try:

--> 241             return findvalue(self._options_values, value, self.equals) if value is not None else None

    242         except ValueError:

/opt/conda/lib/python3.7/site-packages/ipywidgets/widgets/widget_selection.py in findvalue(array, value, compare)

    138     except StopIteration:

--> 139         raise ValueError('%r not in array'%value)

    140 

ValueError: 'id' not in array

During handling of the above exception, another exception occurred:

TraitError                                Traceback (most recent call last)

/opt/conda/lib/python3.7/site-packages/ipywidgets/widgets/widget.py in _handle_msg(self, msg)

    674                 if 'buffer_paths' in data:

    675                     _put_buffers(state, data['buffer_paths'], msg['buffers'])

--> 676                 self.set_state(state)

    677 

    678         # Handle a state request.

/opt/conda/lib/python3.7/site-packages/ipywidgets/widgets/widget.py in set_state(self, sync_data)

    543                     from_json = self.trait_metadata(name, 'from_json',

    544                                                     self._trait_from_json)

--> 545                     self.set_trait(name, from_json(sync_data[name], self))

    546 

    547     def send(self, content, buffers=None):

/opt/conda/lib/python3.7/contextlib.py in __exit__(self, type, value, traceback)

    117         if type is None:

    118             try:

--> 119                 next(self.gen)

    120             except StopIteration:

    121                 return False

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in hold_trait_notifications(self)

   1212                 for changes in cache.values():

   1213                     for change in changes:

-> 1214                         self.notify_change(change)

   1215 

   1216     def _notify_trait(self, name, old_value, new_value):

/opt/conda/lib/python3.7/site-packages/ipywidgets/widgets/widget.py in notify_change(self, change)

    604                 # Send new state to front-end

    605                 self.send_state(key=name)

--> 606         super(Widget, self).notify_change(change)

    607 

    608     def __repr__(self):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in notify_change(self, change)

   1225     def notify_change(self, change):

   1226         """Notify observers of a change event"""

-> 1227         return self._notify_observers(change)

   1228 

   1229     def _notify_observers(self, event):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in _notify_observers(self, event)

   1262                 c = getattr(self, c.name)

   1263 

-> 1264             c(event)

   1265 

   1266     def _add_notifiers(self, handler, name, type):

/opt/conda/lib/python3.7/site-packages/optimade_client/subwidgets/provider_database.py in _observe_providers(self, change)

    191                 self.show_child_dbs.display = "none"

    192                 try:

--> 193                     self.child_dbs.index = 1

    194                 except IndexError:

    195                     pass

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in __set__(self, obj, value)

    602             raise TraitError('The "%s" trait is read-only.' % self.name)

    603         else:

--> 604             self.set(obj, value)

    605 

    606     def _validate(self, obj, value):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in set(self, obj, value)

    591             # we explicitly compare silent to True just in case the equality

    592             # comparison above returns something other than True/False

--> 593             obj._notify_trait(self.name, old_value, new_value)

    594 

    595     def __set__(self, obj, value):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in _notify_trait(self, name, old_value, new_value)

   1220             new=new_value,

   1221             owner=self,

-> 1222             type='change',

   1223         ))

   1224 

/opt/conda/lib/python3.7/site-packages/ipywidgets/widgets/widget.py in notify_change(self, change)

    604                 # Send new state to front-end

    605                 self.send_state(key=name)

--> 606         super(Widget, self).notify_change(change)

    607 

    608     def __repr__(self):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in notify_change(self, change)

   1225     def notify_change(self, change):

   1226         """Notify observers of a change event"""

-> 1227         return self._notify_observers(change)

   1228 

   1229     def _notify_observers(self, event):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in _notify_observers(self, event)

   1262                 c = getattr(self, c.name)

   1263 

-> 1264             c(event)

   1265 

   1266     def _add_notifiers(self, handler, name, type):

/opt/conda/lib/python3.7/site-packages/optimade_client/subwidgets/provider_database.py in _observe_child_dbs(self, change)

    203             self.database = "", None

    204         else:

--> 205             self.database = self.child_dbs._get_grouping_label_value(index)

    206 

    207     @staticmethod

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in __set__(self, obj, value)

    602             raise TraitError('The "%s" trait is read-only.' % self.name)

    603         else:

--> 604             self.set(obj, value)

    605 

    606     def _validate(self, obj, value):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in set(self, obj, value)

    591             # we explicitly compare silent to True just in case the equality

    592             # comparison above returns something other than True/False

--> 593             obj._notify_trait(self.name, old_value, new_value)

    594 

    595     def __set__(self, obj, value):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in _notify_trait(self, name, old_value, new_value)

   1220             new=new_value,

   1221             owner=self,

-> 1222             type='change',

   1223         ))

   1224 

/opt/conda/lib/python3.7/site-packages/ipywidgets/widgets/widget.py in notify_change(self, change)

    604                 # Send new state to front-end

    605                 self.send_state(key=name)

--> 606         super(Widget, self).notify_change(change)

    607 

    608     def __repr__(self):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in notify_change(self, change)

   1225     def notify_change(self, change):

   1226         """Notify observers of a change event"""

-> 1227         return self._notify_observers(change)

   1228 

   1229     def _notify_observers(self, event):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in _notify_observers(self, event)

   1262                 c = getattr(self, c.name)

   1263 

-> 1264             c(event)

   1265 

   1266     def _add_notifiers(self, handler, name, type):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in _update(self, change)

    359         with self._busy_updating():

    360             setattr(self.target[0], self.target[1],

--> 361                     self._transform(change.new))

    362 

    363     def unlink(self):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in __set__(self, obj, value)

    602             raise TraitError('The "%s" trait is read-only.' % self.name)

    603         else:

--> 604             self.set(obj, value)

    605 

    606     def _validate(self, obj, value):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in set(self, obj, value)

    591             # we explicitly compare silent to True just in case the equality

    592             # comparison above returns something other than True/False

--> 593             obj._notify_trait(self.name, old_value, new_value)

    594 

    595     def __set__(self, obj, value):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in _notify_trait(self, name, old_value, new_value)

   1220             new=new_value,

   1221             owner=self,

-> 1222             type='change',

   1223         ))

   1224 

/opt/conda/lib/python3.7/site-packages/ipywidgets/widgets/widget.py in notify_change(self, change)

    604                 # Send new state to front-end

    605                 self.send_state(key=name)

--> 606         super(Widget, self).notify_change(change)

    607 

    608     def __repr__(self):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in notify_change(self, change)

   1225     def notify_change(self, change):

   1226         """Notify observers of a change event"""

-> 1227         return self._notify_observers(change)

   1228 

   1229     def _notify_observers(self, event):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in _notify_observers(self, event)

   1262                 c = getattr(self, c.name)

   1263 

-> 1264             c(event)

   1265 

   1266     def _add_notifiers(self, handler, name, type):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in _update(self, change)

    359         with self._busy_updating():

    360             setattr(self.target[0], self.target[1],

--> 361                     self._transform(change.new))

    362 

    363     def unlink(self):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in __set__(self, obj, value)

    602             raise TraitError('The "%s" trait is read-only.' % self.name)

    603         else:

--> 604             self.set(obj, value)

    605 

    606     def _validate(self, obj, value):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in set(self, obj, value)

    591             # we explicitly compare silent to True just in case the equality

    592             # comparison above returns something other than True/False

--> 593             obj._notify_trait(self.name, old_value, new_value)

    594 

    595     def __set__(self, obj, value):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in _notify_trait(self, name, old_value, new_value)

   1220             new=new_value,

   1221             owner=self,

-> 1222             type='change',

   1223         ))

   1224 

/opt/conda/lib/python3.7/site-packages/ipywidgets/widgets/widget.py in notify_change(self, change)

    604                 # Send new state to front-end

    605                 self.send_state(key=name)

--> 606         super(Widget, self).notify_change(change)

    607 

    608     def __repr__(self):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in notify_change(self, change)

   1225     def notify_change(self, change):

   1226         """Notify observers of a change event"""

-> 1227         return self._notify_observers(change)

   1228 

   1229     def _notify_observers(self, event):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in _notify_observers(self, event)

   1262                 c = getattr(self, c.name)

   1263 

-> 1264             c(event)

   1265 

   1266     def _add_notifiers(self, handler, name, type):

/opt/conda/lib/python3.7/site-packages/optimade_client/query_filter.py in _on_database_select(self, _)

    192                 self.query_button.tooltip = "Search"

    193                 self.sort_selector.valid_fields = sorted(

--> 194                     get_sortable_fields(self.database[1].base_url)

    195                 )

    196                 self.unfreeze()

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in __set__(self, obj, value)

    602             raise TraitError('The "%s" trait is read-only.' % self.name)

    603         else:

--> 604             self.set(obj, value)

    605 

    606     def _validate(self, obj, value):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in set(self, obj, value)

    591             # we explicitly compare silent to True just in case the equality

    592             # comparison above returns something other than True/False

--> 593             obj._notify_trait(self.name, old_value, new_value)

    594 

    595     def __set__(self, obj, value):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in _notify_trait(self, name, old_value, new_value)

   1220             new=new_value,

   1221             owner=self,

-> 1222             type='change',

   1223         ))

   1224 

/opt/conda/lib/python3.7/site-packages/ipywidgets/widgets/widget.py in notify_change(self, change)

    604                 # Send new state to front-end

    605                 self.send_state(key=name)

--> 606         super(Widget, self).notify_change(change)

    607 

    608     def __repr__(self):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in notify_change(self, change)

   1225     def notify_change(self, change):

   1226         """Notify observers of a change event"""

-> 1227         return self._notify_observers(change)

   1228 

   1229     def _notify_observers(self, event):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in _notify_observers(self, event)

   1262                 c = getattr(self, c.name)

   1263 

-> 1264             c(event)

   1265 

   1266     def _add_notifiers(self, handler, name, type):

/opt/conda/lib/python3.7/site-packages/optimade_client/subwidgets/sort_selector.py in _update_drop_options(self, change)

    138         value = self.fields_drop.value

    139         self.fields_drop.options = fields

--> 140         self.fields_drop.value = value

    141         self.fields_drop.layout.width = "auto"

    142 

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in __set__(self, obj, value)

    602             raise TraitError('The "%s" trait is read-only.' % self.name)

    603         else:

--> 604             self.set(obj, value)

    605 

    606     def _validate(self, obj, value):

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in set(self, obj, value)

    576 

    577     def set(self, obj, value):

--> 578         new_value = self._validate(obj, value)

    579         try:

    580             old_value = obj._trait_values[self.name]

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in _validate(self, obj, value)

    610             value = self.validate(obj, value)

    611         if obj._cross_validation_lock is False:

--> 612             value = self._cross_validate(obj, value)

    613         return value

    614 

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in _cross_validate(self, obj, value)

    616         if self.name in obj._trait_validators:

    617             proposal = Bunch({'trait': self, 'value': value, 'owner': obj})

--> 618             value = obj._trait_validators[self.name](obj, proposal)

    619         elif hasattr(obj, '_%s_validate' % self.name):

    620             meth_name = '_%s_validate' % self.name

/opt/conda/lib/python3.7/site-packages/traitlets/traitlets.py in __call__(self, *args, **kwargs)

    973         """Pass `*args` and `**kwargs` to the handler's function if it exists."""

    974         if hasattr(self, 'func'):

--> 975             return self.func(*args, **kwargs)

    976         else:

    977             return self._init_call(*args, **kwargs)

/opt/conda/lib/python3.7/site-packages/ipywidgets/widgets/widget_selection.py in _validate_value(self, proposal)

    241             return findvalue(self._options_values, value, self.equals) if value is not None else None

    242         except ValueError:

--> 243             raise TraitError('Invalid selection: value not found')

    244 

    245     @observe('value')

TraitError: Invalid selection: value not found

**To Reproduce**
Steps to reproduce the behavior:
1. Start a new calculation.
2. Go to the Structure selection step and select the OPTIMADE tab.
3. Select the JARVIS provider.

**Version (if known)**
- App version: [e.g. v21.11.0]

**Additional context**

When trying to create an automated bug report, I got the following message from GitHub:

Will open a separate issue for this.