Fix building with Poppler 0.26.02

Adapted from [1] with changes to make it backwards-compatible with older versions of Poppler.

[1] github.com/OpenMandrivaAssociation/inkscape/blob/master/inkscape-poppler-26.02.patch#L29

Credits: Bernhard Rosenkränzer bero@lindev.ch

Fixes #6054 (closed)