PushPull FileRetrievalSystem NPE if mime comment for type doesn't include ampersand

CAS Push Pull throws an NPE in its FileRetrievalSystem when it tries to parse metadata from MIME comment without ampersands – it expects the ampersands to be there apparently to separate additional metadata information to pass along and doesn't deal with the case in which the comment in the MIME type doesn't include those extra params. This is a blocker and effectively blocks nominal use of Push Pull.