Manual testing - tst_barstest crashes

In the manual test tst_barstest, the application crashes if you left-click "Test primary series" 6 times. The fault lies in step 5 of the "primary series" test, "Remove nonexistent series".

Steps to reproduce:

Left-click "Test primary series" 6 times. The application output will show step 0 up to step 5, and the application will crash at step 5 of this primary series test.

Expected behavior:

Removal of a nonexistent series should not result in a crash.

Observed behavior:

Removal of a nonexistent series results in a crash during step 5 of the "primary series" test in tst_barstest.