Fix for handling empty code block in doc comments

[davidBar-On]

Suggested fix for issue #4793 for handling empty code block in doc comments (replacing PR #4895). If the doc comments code block includes only empty lines than the output is one line with empty code (///). If no code line was included between the two ///''' then the output also does not include any code line.

A simpler solution could be to add trim() here, i.e to make it _ if self.code_block_buffer.trim().is_empty() =>.... however it seem that changing format_code_block() is more robust.

[ytmimi]

@davidBar-On sorry that this has been sitting around in the backlog for so long. I took a look at this and I like your second proposed fix of adding .trim() to the guard clause. I think it's fine to remove all lines from an empty code block if the user has specified format_code_in_doc_comments=true.

I'm noticing that this PR is against the stbu branch instead of master. Maybe you could close this and open up a new PR against master with the simplified implementation. The code in master is slightly different, but the simplified fix you described above should be the same!

[davidBar-On]

Created PR #5601 that trims the empty code block as discussed, and closing this PR.