Fixed: AttributeError when params is None.

[sbywater]

Without this, AttributeError is thrown when params is None.

[sbywater]

Actually it throws "TypeError: argument of type 'NoneType' is not iterable" not AttributeError.

[euske]

Sorry for a very late reply. I appreciate the fix, but I don't understand when params becomes None. The other fixes seem a bit kludge-y and only applicable to rare erroneous PDFs.

[bartromgens]

I encountered the same error: "TypeError: argument of type 'NoneType' is not iterable" when converting the following pdf to text: https://www.tweedekamer.nl/downloads/document?id=61a2686e-ec4a-4881-892b-04e215462ecd&title=Besluitenlijst%20extra%20procedurevergadering%20IM%20d.d.%207%20juni%202011.pdf

If this is a erroneous PDF, I am more than happy to deal with that. I don't have any experience with pdfminer, so don't know why params is None.

Just reporting this because it might help fix the issue. Happy to provide more details if needed.