It looks like a bug, and also I remember fixing a similar problem (tdf#135997) in one of earlier versions. It was related to the recent used characters list that is shown in the widget on the toolbar; and an easy solution was to reset user profile, which removed every user setting including the recent used list.
However, for the proper fix, I suggest you to send a crash report (if it is suggested to you after the crash), and mention its address in the mentioned tdf#135997.
And also it could help if you send a copy of your problematic user profile there to the bug report, - maybe it would enable us to reproduce, which then would let us fix it properly.