### Link to issue number:

Fixes nvaccess#17198

 ### Summary of the issue:

When using the Microsoft Pinyin Input Method for Chinese and enabling
the Pinyin compatibility option to use the previous version, typing in
LibreOffice (e.g. Writer or Calc) while an IME popup was showing
triggered an error, with this traceback:

    ERROR - eventHandler.executeEvent (10:45:49.378) - MainThread (7416):
    error executing event: caret on <NVDAObjects.Dynamic_SymphonyParagraphSymphonyTextEditableTextWithAutoSelectDetectionIAccessible object at 0x0B918DF0> with extra args of {}
    Traceback (most recent call last):
      File "eventHandler.py", line 353, in executeEvent
        _EventExecuter(eventName, obj, kwargs)
      File "eventHandler.py", line 119, in __init__
        self.next()
      File "eventHandler.py", line 128, in next
        return func(*args, **self.kwargs)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "compoundDocuments.py", line 548, in event_caret
        caret = self.makeTextInfo(textInfos.POSITION_CARET)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "documentBase.py", line 76, in makeTextInfo
        return self.TextInfo(self, position)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "compoundDocuments.py", line 287, in __init__
        self._start = self._end = self._startObj.makeTextInfo(position)
                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "documentBase.py", line 76, in makeTextInfo
        return self.TextInfo(self, position)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "textInfos\offsets.py", line 505, in __init__
        self._startOffset = self._endOffset = self._getCaretOffset()
                                              ^^^^^^^^^^^^^^^^^^^^^^
      File "textInfos\offsets.py", line 267, in _getCaretOffset
        raise NotImplementedError
    NotImplementedError

This was caused by the attempt to create a text info
for an object from the IME popup that's not actually part
of the LibreOffice accessibility tree, and that doesn't provide
any means to get the current caret position.

This is due to `CompoundDocument._get_caretObject`
returning the last queued focus object, which isn't necessarily
the object that the caret change event has actually been sent for,
and might be an object that doesn't support reporting of a caret positiion
altogether.

 ### Description of user facing changes

When using the Microsoft Pinyin Input Method for Chinese and enabling
the Pinyin compatibility option to use the previous version, typing in
LibreOffice (and potentially other applications) while an IME popup is
showing no longer triggers an error.

 ### Description of development approach

Handle the NotImplementedError error that may get thrown
in CompoundDocument.event_caret.

 ### Testing strategy:

1. set up the Microsoft Pinyin Input Method for Chinese and enable
   the Pinyin compatibility option as described in issue nvaccess#17198
2. start LibreOffice Writer
3. start typing, e.g. just type "e" multiple times
4. Notice the IME popup showing without triggering
   an error

 ### Known issues with pull request:

None.

 ### Code Review Checklist:

- [x] Documentation:
  - Change log entry
  - User Documentation
  - Developer / Technical Documentation
  - Context sensitive help for GUI changes
- [x] Testing:
  - Unit tests
  - System (end to end) tests
  - Manual testing
- [x] UX of all users considered:
  - Speech
  - Braille
  - Low Vision
  - Different web browsers
  - Localization in other languages / culture than English
- [x] API is compatible with existing add-ons.
- [x] Security precautions taken.

* Explicitly mention Writer, there are still more errors with Calc
  with the old Microsoft Pinyin version,
  see nvaccess#17198 (comment)
* Move entry to the "Bug Fixes" section. This is not a new feature.