QtCreator crashes when adding class in quick succession

Steps to reproduce:

• Open QtCreator and create a new application/library project
• In quick succession, add a new class followed by another
• QtCreator crashes with SIGSEGV

This crash seems to occur if you try to add a class whilst QtCreator is still internally processing the addition of the previous class (ie trying to run qmake etc).  If you wait ~30 seconds between adding classes, the crash does not occur.

I had previously considered this a non issue thinking that adding classes in quick succession was not really a common thing to do, but since then I've revised that thought.  As such this issue has been around for a few versions of QtCreator (back to 4.5.0 at least).

The attached backtrace was generated from a debug build of QtCreator from git branch 4.7.