Created attachment 36452 [details] test-data/slideshow/gradient-fill-in-group.pptx I found an edge case where calling getFillColor on a shape which calls getFillPaint throws a NullPointerException. The fill of the shape is gradient fill, but the CTGradientStopList is null. Attached example pptx, test case, and the fix.
Created attachment 36453 [details] test case and fix for bug63200
Thanks for the patch, applied via r1854639 with some more changes that were visible in our integration-tests via this sample file.