400 error from behaviours validators.json when on Requirements for Jira page

1. Download the Requirements for JIRA add-on
2. View a project from the R4J menu
   
3. Behaviours throw an error in the browser console

rest/scriptrunner/behaviours/latest/validators.json [c.o.j.behaviours.restservice.BehavioursEndpoint] REST /behaviours/validators should not be called with a null issueId. Possible BUG

This seems to be the same problem that occurred in ---SRJIRA-1883--- when viewing Tempo Timesheets forms. Behaviours are not compatible with R4J, therefore it does make sense that a call to validators.json will return an error.

This does not affect the functionality of behaviours or anything else - it just causes an error message in the browser console. The user requests that we prevent the error from being thrown.