When importing from CSV, the import successfully created users, components etc but when it attempted to create issues a Null Pointer Exception was produced, from ExternalUtils.addOption().

It turns out it was to do with a custom field only being applicable to certain types of Issues, and our data contained a value for that custom field in an issue of the wrong type.

It would be good if there was a more informative error message than just a Null Pointer Exception when this occurs.