[Cairo] cairo_restore leaves cairo_t in invalid state with status 0

[Carl Worth]

On Sep 13, Keith Packard wrote:
 > Call cairo_restore without ever calling cairo_save and you pop the gstate 
 > off the list, leaving it NULL.  Try to invoke any cairo function that uses 
 > gstate and you get a segfault.

Yes, and the proposed fix is correct and committed.

Thanks,

-Carl