ProjectExplorer: Removing the only configured (temporary) kit results in bad Projects view

Steps to reproduce:

• have an already built project somewhere
• ensure you're not having the kit configured (or its Qt version) used to build the above mentioned project
• remove the respective .user file (if the project had been built with this QC)
• open the project and import it (using the build directory)
  • ensure this creates the respective Qt version and Kit..
• ensure you're not using any additional kit when configuring
• after configuring, go to the settings -> B & R -> Kits and remove the kit
  • this will leave the project now 'unconfigured', so switch to Projects view

Current result:

• the removed (temporary) Kit is still displayed
  • I'm not sure if this is correct at all [I had 2 kits + the temporary], after removing the temporary from settings and heading back to the Projects view there are only 2 kits listed (the temporary and a second kit, but my default kit is missing - but still available on the left side (see Note below)
• I wasn't able to turn the "Configure Project.." into an enabled state - no matter whether checking an existing (and working) kit or using the non-existing (but listed) temporary

Note:

• double click on one of the greyed out kits on the left bar below the current unconfigured project makes the project turn into configured state and gets rid of the unconfigured project settings page

When removing the only used kit from the settings I got a 

SOFT ASSERT: "k" in file /work/build/qt-creator/src/plugins/projectexplorer/targetsettingspanel.cpp, line 311

on the command line.