I just got the FITS viewer to kill KStars 3.1.1 (build 2019-03-09). It's on Kubuntu 18.04 Dell laptop and up to date OS and KStars/INDI from PPA. Now simply start KStars and open a FITS file. Then click the histogram tool and then the Statistics tool, histogram, stats, histogram, stats. After more or less switches I get a segfault. See the debugger output in attachment.
EDIT: Perhaps you need to maximize the viewer window too in order to see the segfault!
I attached a screen recording. When I'm stubborn enough, it always crashes sooner or later. The video implies that this is a minor issue as I had to switch quite often but when I first encountered it, it crashed real soon.