Automation - NPE exception in Fn.getVocabularyLabel on missing key

When using the Fn.getVocabularyLabel function in the "Run script" operation with a key that does not exist, a NPE exception is thrown.

here is an example:
Context["LABEL"]=Fn.getVocabularyLabel("VOC","KEY");
where KEY does not exist in the vocabulary VOC.

Attached is the relevant part of the server log.