Steps to reproduce:

1. Make a template 1 with only host group 1. Template 1 should be only in host group 1 and not in any other.
2. Go to Host groups and move template1 from host group1 to host group 2 (using only "to right" arrow in the frontend).
3. Click "update".

Result:
Error message is shown:
Template "Template 1" cannot be without host group.
Expected:
Template is moved to host group 2 and participation in host group 1 is gone.

Regards,
Oleg