Undefined return value at casetracker_case_state_save()

After running tests there were 6 warnings with the following message:

Undefined variable: result	Notice	casetracker.module	642	casetracker_case_state_save()

This occurs because casetracker_case_state_save() returns a non defined variable (which luckily is not expected by the caller). Removing that return statement makes tests pass without any warnings.