Address 4043

[JorjMcKie]

When duplicating a page without /Contents objects, make sure to detect this situation.
Addresses issue 4043.

[julian-smith-artifex-com]

JM_read_contents() seems to return either a mupdf buffer if contents is array, or a bytes/str (from pdf_load_stream()) or empty bytes. So isn't it possible for if res and res.m_internal: to still fail if res is non-empty str or bytes?

[JorjMcKie]

Yes, I am aware of that problem. The return is always one of 2 alternatives:

• an mupdf.FzBuffer in all cases where the page has /Contents at all,
• otherwise an empty bytes object.
  So a really clean solution should be one of the following:
• A FzBuffer of either length 0 - or length 1 containing b" ".
• None - which I would prefer as it reflects the facts in the best way.

[JorjMcKie]

Your opinion?

[julian-smith-artifex-com]

Ah yes, i misread pdf_load_stream() as returning a char*. Agree that returning None would be better than b"" but that can be fixed in future.