ikhal crashes when creating new event with filtered calendars

Describe the bug
When opening ikhal with the -a-argument set to something other than the default it crashes when trying to create a new calendar entry.

If applicable: Stack Trace

Traceback (most recent call last):
  File "/usr/lib/python3.12/site-packages/khal/ui/__init__.py", line 1363, in start_pane
    loop.run()
  File "/usr/lib/python3.12/site-packages/urwid/event_loop/main_loop.py", line 337, in run
    self._run()
  File "/usr/lib/python3.12/site-packages/urwid/event_loop/main_loop.py", line 439, in _run
    self.event_loop.run()
  File "/usr/lib/python3.12/site-packages/urwid/event_loop/select_loop.py", line 182, in run
    self._loop()
  File "/usr/lib/python3.12/site-packages/urwid/event_loop/select_loop.py", line 229, in _loop
    record.data()
  File "/usr/lib/python3.12/site-packages/urwid/display/_posix_raw_display.py", line 273, in wrapper
    return self.parse_input(event_loop, callback, self.get_available_raw_input())
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/display/_raw_display_base.py", line 488, in parse_input
    callback(decoded_codes, raw_codes)
  File "/usr/lib/python3.12/site-packages/urwid/event_loop/main_loop.py", line 466, in _update
    self.process_input(keys)
  File "/usr/lib/python3.12/site-packages/urwid/event_loop/main_loop.py", line 566, in process_input
    handled_key = self._topmost_widget.keypress(self.screen_size, key)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/popup.py", line 143, in keypress
    return self._current_widget.keypress(size, key)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/frame.py", line 526, in keypress
    return self.body.keypress((maxcol, remaining), key)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/khal/ui/__init__.py", line 1123, in keypress
    return super().keypress(size, key)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/khal/ui/base.py", line 114, in keypress
    return super().keypress(size, key)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/widget.py", line 729, in keypress
    return get_delegate(self).keypress(size, key)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/khal/ui/widgets.py", line 313, in keypress
    key = super().keypress(size, key)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/columns.py", line 1216, in keypress
    key = w.keypress(size_args[i], key)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/widget.py", line 729, in keypress
    return get_delegate(self).keypress(size, key)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/widget.py", line 729, in keypress
    return get_delegate(self).keypress(size, key)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/frame.py", line 526, in keypress
    return self.body.keypress((maxcol, remaining), key)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/khal/ui/calendarwidget.py", line 330, in keypress
    return self.on_press[key](start, end)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/khal/ui/__init__.py", line 1177, in new_event
    self.eventscolumn.original_widget.new(date, end)
  File "/usr/lib/python3.12/site-packages/khal/ui/__init__.py", line 895, in new
    self.edit(event)
  File "/usr/lib/python3.12/site-packages/khal/ui/__init__.py", line 762, in edit
    editor = EventEditor(self.pane, event, update_colors, always_save=always_save)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/khal/ui/editor.py", line 374, in __init__
    self.collection._calendars[self.event.calendar],
    ~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^
KeyError: 'personal'

(Note: personal is my configured default, and is not included in the calendars to display)

To Reproduce
Steps to reproduce the behavior:

• Configure khal with multiple calendars
• Set one (cal1) as the default
• Open ikhal filtering for another one: ikhal -a cal2
• Try to create a new date

Expected behavior
I can create a new appointment, with either cal2 or no calendar selected (In case of multiple calendars being included" any of them/none of them)

OS, version, khal version and how you installed it:

• The output of khal --version: khal, version 0.11.3
• Installation method: Archlinux Repo
• python version: 3.12.7
• OS: Archlinux
• Your khal config file:

[calendars]
    [[personal]]
        path = ~/.local/share/vdirsyncer/calendar/personal
    [[voltstock]]
        path = ~/.local/share/vdirsyncer/ws_calendar/voltstock-infos-1/
  (<Stripped: Some more calendars>)

[locale]
    weeknumbers = left
    unicode_symbols = False
    longdateformat = %Y-%m-%d
    longdatetimeformat = %Y-%m-%d %H:%M
    datetimeformat = %m-%d %H:%M
    dateformat = %m-%d
    firstweekday = 0

[default]
    default_calendar = personal
    timedelta = 3d

Start in khal/ui/editor.py at EventEditor.init, then trace the new-event path through khal/ui/init.py and reproduce with ikhal -a cal2. Verify that creating an event with a filtered calendar no longer raises the reported KeyError and allows the expected calendar selection or no calendar.