Target Setup Page may crash QC

Steps to reproduce:

• have 2 valid kits available
• have an existing project without *.user file
• open it and select both kits for on the target setup page, hit Configure
  • you should be on Edit mode now
• build it once (not sure if necessary)
• go to Options -> Kits
• set all compilers of the kits to None
• hit OK
• go to Project view
  • this should look bad now
• go to Options -> Kits
• remove both kits (starting with the default one)
• hit OK

Current result:

• QC crashes (I could not reliably reproduce but got back traces - see attachment)

Seems the handleTargetChanged() signal may be processed too late (after the handleTargetRemoved() had been processed already and the target does no more exist)