Error in Groovy script email sending

[JeffJ]

I'm getting the following error in the log when I try to send an email using the built in script runner 'send a custom email' as a test:

2014-01-31 11:54:26,480 Thread-54 WARN *myusername* 714x580x1 1b8240l *ouripadddress* /secure/admin/groovy/CannedScriptRunner.jspa [groovy.canned.utils.WorkflowUtils] This is a bug in the code - you should only see this when previewing. Returning current user

Exception in thread "Thread-54" org.codehaus.groovy.runtime.typehandling.GroovyCastException: Cannot cast object 'com.atlassian.jira.event.issue.IssueEvent@639e361b[issue=SPKHD-457,comment=<null>,worklog=<null>,changelog=<null>,eventTypeId=1,sendMail=true,params={},subtasksUpdated=false]' with class 'java.lang.String' to class 'com.atlassian.jira.event.issue.IssueEvent'

[JamieA]

As it says, it's a bug ;-) It should only happen in the admin screens, not when it's actually configured as a workflow function or listener.

[JeffJ]

Fair enough... It's just weird because it's definitely worked before and I don't know what changed.

[JamieA]

It happens when you preview, there's an error, you preview again, something like that.

[JeffJ]

So, okay, the error is only supposed to occur when I'm previewing.. but thats the error I get when I run it. I don't actually get the error on preview.