Fix(revit): Null check before attempt to override view options

[oguzhankoral]

I remember @didimitrie you were fixing an issue on forum while implementing OverrideViewOptions function, i believe what i did shouldn't effect what you have done before, but would be nice if you can test that behavior.

BEFORE

AFTER

[linear]

CNX-984 Only one object fails to convert from Revit

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Project coverage is 9.17%. Comparing base (b5b9d06) to head (020f8f3).
Report is 1 commits behind head on dev.

Files with missing lines	Patch %	Lines
...rters.RevitShared/Helpers/DisplayValueExtractor.cs	0.00%	6 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##             dev    #474   +/-   ##
=====================================
  Coverage   9.16%   9.17%           
=====================================
  Files        228     228           
  Lines       4297    4296    -1     
  Branches     544     542    -2     
=====================================
  Hits         394     394           
+ Misses      3887    3886    -1     
  Partials      16      16           

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