Error deleting association with Test (moved to other issue type) from Test Set

Steps to reproduce:
1) Create XRay test
2) Create XRay test set and Add the already created xray test
3) Go back to XRay test and "Move" test from Xray test type to Bug issue type
4) It is possible to change issue type but test is still part of Test set
5) When I create test execution and want to add this Test Set there is error
6) If I go back to Test Set it is not possible to "Remove" this test from test set (only possibility is to change issue type back to XRay test and remove it)