Fix up of: Fix up of: Don't announce 'selected' when the focus moves in Google sheets if the focused cell is the only cell selected (#8898)

[JulienCochuyt]

Link to issue number:

Fixes #9520
Fixes #7292 (comment) (only the error log in the comment, not the whole issue).
Faulty behavior introduced as of b02ed2d (#8898)

Summary of the issue:

MSHTML._get_table historically raises a NotImplementedError when there is no surrounding table.
IAccessible._get_table, on the other hand, returns None in the same situation.
IAccessible._get_selectionContainer, introduced by b02ed2d, calls self.table which can lead to the following error log:

ERROR - queueHandler.flushQueue (13:44:56.473):
Error in func _loadBufferDone from eventQueue
Traceback (most recent call last):
  File "queueHandler.pyo", line 53, in flushQueue
  File "virtualBuffers\__init__.pyo", line 464, in _loadBufferDone
  File "browseMode.pyo", line 1190, in event_treeInterceptor_gainFocus
  File "browseMode.pyo", line 1513, in event_gainFocus
  File "browseMode.pyo", line 1190, in <lambda>
  File "NVDAObjects\__init__.pyo", line 1030, in event_gainFocus
  File "NVDAObjects\__init__.pyo", line 918, in reportFocus
  File "speech.pyo", line 416, in speakObject
  File "speech.pyo", line 340, in speakObjectProperties
  File "baseObject.pyo", line 47, in __get__
  File "baseObject.pyo", line 147, in _getPropertyViaCache
  File "NVDAObjects\IAccessible\__init__.pyo", line 1265, in _get_selectionContainer
  File "baseObject.pyo", line 47, in __get__
  File "baseObject.pyo", line 147, in _getPropertyViaCache
  File "NVDAObjects\IAccessible\MSHTML.pyo", line 957, in _get_table
NotImplementedError

Description of how this pull request fixes the issue:

Return None instead of raising NotImplementedError in MSHTML._get_table, in coherence with its base class.

Testing performed:

Browsed with IE11 under Windows 10 to (http://www.w3.org/TR/wai-aria-practices/examples/tabs/tabs-1/tabs.html) (which is the test case of #9520 and report focus on the example tab header.

Known issues with pull request:

This approach can theoretically break existing assumption of the method raising the exception, but other IAccessible implementation have been recently much more tested and return None in the same case.
So, I guess it is safer to apply the proposed change than to track every single call to _get_table and enclose in a try...except block, with the risk of missing a few of them in the process.

Change log entry:

Section: Bug fixes

NVDA is no longer silent when focusing an HTML tab header in Internet Explorer.

[JulienCochuyt]

b464c43: Rebased onto latest master.

[JulienCochuyt]

cc @michaelDCurran, @feerrenrut

[Adriani90]

@JulienCochuyt strangely this PR seems closed by you but in Github insights it appears like it is still open. So is this still valid? Are you working on it?

[JulienCochuyt]

@JulienCochuyt strangely this PR seems closed by you but in Github insights it appears like it is still open. So is this still valid? Are you working on it?

The branch has erroneously been pruned while syncing our fork.
I am closing this PR and reopening a new one with the same fix rebased onto latest master.

[JulienCochuyt]

Reopened as PR #10080