Bug report: Application crashed with TypeError

## Automated report

_This issue was created with the app's automated bug reporting feature.
Attached to this issue is the full traceback as well as an environment
fingerprint that contains information about the operating system as well as all
installed libraries._

## Additional comments (optional):

I imported a calculation done by my colleague on the QuantumEspresso app. After that, I open the corresponding results on the QE App. When I try to view "Electronic Bands + PDOS, the app crashes and i cannot view the bands.

## Attachments

Traceback

```python-traceback
~/.local/lib/python3.9/site-packages/aiidalab_qe/common/bands_pdos/bandpdoswidget.py in render(self)
306 self.rendered = True
307
--> 308 self._initial_plot()
309 self._toggle_projection_controls()
310 self._toggle_pdos_options()

~/.local/lib/python3.9/site-packages/aiidalab_qe/common/bands_pdos/bandpdoswidget.py in _initial_plot(self)
318 def _initial_plot(self):
319 """Create the initial plot."""
--> 320 self._model.fetch_data()
321 self._model.create_plot()
322 self.plot = self._model.plot

~/.local/lib/python3.9/site-packages/aiidalab_qe/common/bands_pdos/model.py in fetch_data(self)
147 if self.bands:
148 if not self.bands_data:
--> 149 self.bands_data = self._get_bands_data(self.bands)
150 if not self.external_bands_data:
151 for key, bands_data in self.external_bands.items():

~/.local/lib/python3.9/site-packages/aiidalab_qe/common/bands_pdos/model.py in _get_bands_data(self, bands)
249 return None
250
--> 251 bands_data = get_bands_data(bands)
252 return bands_data
253

~/.local/lib/python3.9/site-packages/aiidalab_qe/common/bands_pdos/utils.py in get_bands_data(outputs, fermi_energy)
99 )
100 # The fermi energy from band calculation is not robust.
--> 101 if "fermi_energy_up" in outputs.band_parameters:
102 bands_data["fermi_energy_up"] = outputs.band_parameters["fermi_energy_up"]
103 bands_data["fermi_energy_down"] = outputs.band_parameters["fermi_energy_down"]

TypeError: argument of type 'Data' is not iterable
```

Environment fingerprint

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**By submitting this issue I confirm that I am aware that this information can
potentially be used to determine what kind of calculation was performed at the
time of error.**