Today I wanted to attempt to track down what may be causing kwin to crash consistently for me on first login. So, I created a new user. In doing so I found that no default apps were created in the "Favorites" portion of the menu. So, I tried to go about adding apps to favorites by right clicking on them. The result was no dialog box would appear and then after a short time plasma-shell would crash. This happens on 3 systems I've tested.
The abrt process reports this as a dup of https://bugzilla.redhat.com/show_bug.cgi?id=1313419
It always happens for me so I wonder if it happens for others.