No reaction when clicking "new shape" button

[SvenLieber]

That's a tricky one! Not always possible to reproduce.

I had this bug two times when doing the following:

1. Load example data
2. Move some shapes around with drag and drop
3. Clear page
4. Click validate (console obviously shows an error)
5. Click import data
6. Close the open file dialog (two times, because sometimes it appears two times, see Double open file dialog #231 )
7. Click on + Shape

Now in some cases a shape is created. But sometimes nothing happens, i.e. no shape is created. There is also no error message.