When debugging a flow service, on calling another flow service an error dialog popped up stating a null pointer exception had occurred. No other information was displayed. On dismissing the dialog, the debugging session terminated.
This did not occur when running the same flow service, nor did it occur on all flow service calls.
While trying to debug the problem, I selected ‘Validate Input’ on the flow service being called, then saved the service. The call to the flow service ceased throwing the error. I then deselected ‘Validate Input’, and saved the file. The error did not come back.
I’m still trying to figure out what caused the issue, but if you experience the problem, try editing the flow service and saving it.