The logic is simple:
"If Original Fix Version is null and Fix Version is not null, set Original Fix Version to Fix Version."
I can get the value of Fix Version/s using "issue.fixVersions".
I can get the value of Original Fix Version using "issue.getCustomFieldValue"
I am running this in Listener, and I get this output in the log:
WARN [runner.AbstractScriptRunner]: orgFixVersionFieldValue = null
WARN [runner.AbstractScriptRunner]: fixVersionValue = [5.1]
WARN [runner.AbstractScriptRunner]: Setting new orgFixVersionField
WARN [runner.AbstractScriptRunner]: new orgFixVersionFieldValue = [5.1]
But when I go to look at the Original Fix Version in the project, it is still null.