[cairo] Win32 assert: state->image != NULL

[Chris Wilson]

Excerpts from Damian Frank's message of Thu Aug 20 18:44:48 +0100 2009:
> Does anyone know what this assert means?  I keep seeing it when running
> 1.9.3 on windows.

It means that we attempted to perform a fallback operation with zero
extents. I was confident that I had managed to eliminate that possibility
with the reworked clipping (hence why it became an assertion).

Apparently, I failed.

This could either be in the extents checking, or in the conversion of
win32 over to the new clipping method.  If you have a simple test case,
that would be useful for me to step through and see where I made the
mistake.

Damian, thanks again for all the bug reporting and patches! :)
Hopefully we'll be back to having fun in no time.
-ickle