'T-Shirt Sizes' cardset incorrectly selectable in Planning with Issue-Tracker mode

[Dan1elBox]

Describe the bug
Within the wizard, in certain edge cases, it is possible to select the 'T-Shirt sizes' card set when using 'Planning with Issue-Tracker' mode

To Reproduce
Steps to reproduce the behavior:

1. Choose either the 'Planning without User Stories' or the 'Planning with User Stories' mode, choose the
   "T-shirt sizes"-Cardset and navigate to the final wizard step (but do not create the session yet!)
2. Navigate back to step 1 and select the 'Planning with Issue-Tracker' mode
3. Notice that in 'Planning with Issue-Tracker' mode, you can now also use the T-shirt size card set, even though this should not be allowed!