Issue #454: Crash: using CRTL+Z while using line tool (dismine/valentina)

New issue 454: Crash: using CRTL+Z while using line tool https://bitbucket.org/valentinateam/valentina/issues/454/crash-using-crtl-z-while-using-line-tool

Robin Lilian:

This has happened two times now: I start using the “point on a line” tool by clicking on the first point. I realise I wanted to do something else and try to abort by pressing CRTL+Z (“go back”). Of course this shouldn’t do anything. Instead, the program crashes. I’m using 0.4.2.