NullPointerException when trying to run tests

I haven't run any tests in a few weeks, but before that there were no problems. I tried it again today, but now I get Error 500 whenever I click on "Run" to run tests.
I tried running tests from different Test and Test Execution issues, but the result is the same. The URL after clicking is /secure/XrayExecuteTest!default.jspa?testExecIssueKey=SAN-97&testIssueKey=SAN-95
It is possible to change the Status of the Test when I'm in Test or Test Execution view and choose "Pass", "Fail" etc in the dropdown menu where also the Run link is.
I would submit an error log, but I can't seem to be able to do that, so I'll paste the start of the stack here:
java.lang.NullPointerException
java.lang.NullPointerException
at com.xpandit.raven.webwork.TestRunAction.initTestTypeParameters(Unknown Source)
at com.xpandit.raven.webwork.TestRunAction.doDefault(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)