fix: ParsrConverter fails on pages without text

[anakin87]

Related Issues

• fixes ParsrConverter invalid if statement #3593

Proposed Changes:

Since #2932, the form feed character ("\f") is used to separate different pages.
In the ParsConverter, for each page, there is this check:

haystack/haystack/nodes/file_converter/parsr.py

Lines 189 to 190 in dc26e6d

	if text[-1] != "\f":
	text += "\f"

that raises an error if len(text)==0. For example, we can have empty pages or pages where there is only a table.
I corrected this little bug.

How did you test it?

Manual test using this PDF.

Notes for the reviewer

I also have doubts about

haystack/haystack/nodes/file_converter/parsr.py

Line 210 in dc26e6d

docs = tables + [Document(content=text.strip(), meta=meta, id_hash_keys=id_hash_keys)]

If the first page is blank, "\f" is stripped and page numbers may become incorrect.
@bogdankostic WDYT?

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added tests that demonstrate the correct behavior of the change
• I've used the conventional commit convention for my PR title
• I documented my code
• I ran pre-commit hooks and fixed any issue

[julian-risch]

The change looks good to me and the PR is ready to be merged.
Sidenote: When I reviewed the PR, I also came across this line of code

haystack/haystack/nodes/file_converter/parsr.py

Line 155 in eb9d3fc

while status_response.status_code == 200 and status_response.status_code != 201:

This could be simplified by having just

while status_response.status_code == 200

Maybe that's something for you @bogdankostic to check when you also have a look at

haystack/haystack/nodes/file_converter/parsr.py

Line 210 in dc26e6d

docs = tables + [Document(content=text.strip(), meta=meta, id_hash_keys=id_hash_keys)]

and empty documents, wrong page numbers?