[FIX] Concatenate: fix source ID as class problem

[krystofair]

Using OWConcatenate with option add SourceID to classVar and ignore names from other table raise exception.

Issue

Fixes #7323

Description of changes

Make this IF branch working.

Includes

• Code changes
• Tests
• Documentation

[codecov]

Codecov Report

❌ Patch coverage is 28.57143% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.98%. Comparing base (eea7a75) to head (265e98c).

❌ Your patch check has failed because the patch coverage (28.57%) is below the target coverage (95.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7324   +/-   ##
=======================================
  Coverage   88.98%   88.98%           
=======================================
  Files         337      337           
  Lines       74598    74603    +5     
=======================================
+ Hits        66378    66387    +9     
+ Misses       8220     8216    -4     

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[markotoplak]

Thanks for the PR. I close it in favor of #7340. The code in this PR is a substantial departure from the existing logic, and I'd rather stay closer to it. One of the differences that the "old" logic handles better are subclasses of Table (such as Corpus). Also, the proposed logic was a bit complex.