Started gnome-help-browser. Running on small (640x480) screen so attempted to get rid of toolbar. Couldn't remember how. Tried clicking and double-clicking on the left-hand bit of the toolbar (which you'd actually use to drag the toolbar somewhere). Nothing happened. Clicked a lot more, very fast, here. Moved mouse infinitesmally whilst doing this. Bang! Backtrace attached.
Created attachment 1211 [details] crappy backtrace of gnome-help-browser crash (stripped, so few symbols)
Does this still happen for you? I can't reproduce it here (on a 1024x768 display).
I can't reproduce this either, fwiw.