Handle COMError when fetching table header cells in Word documents

[bramd]

Link to issue number:

Fixes #6827

Summary of the issue:

Sometimes there is a reference to a COM object in _curHeaderCellTrackerTable, but the object throws a COMError on accessing one of it's properties, such as range.
Especially in Outlook this problem occurs if an email containing a table has been opened and the user closes that email and opens another email containing tables.
The unhandled COMError prevented the user from reading the email/document.

Description of how this pull request fixes the issue:

Handle the COMError.

Testing performed:

Tested on Outlook 2016.

Known issues with pull request:

None.

Change log entry:

• Bug fixes
  • Prevent errors while reading emails containing tables in Microsoft Outlook (Unable to read tables in Outlook 2016 #6827)

[LeonarddeR]

I belief the if not self._curHeaderCellTrackerTable will alreade be dealt with if the lines above raise an AttributeError. Honestly, I'd check for if not self._curHeaderCellTrackerTable before executing the try statement, which looks somewhat cleaner. I leave it up to you.

[bramd]

You're right, the first part of this or statement is unneeded. I removed it and left the try/except intact. Removing the except AttributeError and solving this in an if statement would introduce another variable to hold state, or a level of nested if statements. I think having all the logic in a single try/except makes the code easier to read.