skip split on 'none of the sources'

magic/conversational.py

@@ -36,7 +36,7 @@ async def question_handler(question: Question, state: State) -> Answer:
     logger.info(f"Sources: {sources}")
     if sources:
         sources = re.findall(COURSE_PATTERN, sources)
-    else:
+    elif "none of the sources" not in answer.lower():
         answer, sources = split_sources(answer)
 
     courses = [source.upper() for source in sources if state.course_exists(source)] # filter out courses that don't exist