Mollweide plotting error for bounds on pole

[pwolfram]

The Mollweide projection cannot handle geometry plotted exactly on a pole, e.g., via this script at https://gist.github.com/pwolfram/d1c3f1bf513caf24ce6d3a3a0362ea6c for different bounding polygons:

[-180,-60,180,60]:

[-180,-90,180,-60]:

[-180,-89,180,-60]:

This is likely related to #724.

cc @xylar