Comment # 4 on bug 99464 from Tobias Klausmann

The mentioned workaround in the original description got adapted and committed
recently:

c3486cd8c9092cbe33dfc77b906e2475b1e32c8d st/mesa: do not call
update_framebuffer_size with NULL pointer

This should fix at least the SEGV. Maybe it can be reported if the invisible
mouse pointer still exists in newer versions of mesa!