MdTag "MD:Z:0" not handled correctly

Wanted to bring this up, the tag "MD:Z:0" is parsed in correctly, with no matches, mismatches, or deletions, but unfortunately tag.start() will throw an error as there are no matches and so will toString (which depends on start)  

This occurs if the Cigar is something like "101I", 101 inserted bases.

As far as I can see, there is no way to compute the start position from this other than saving the original start somewhere, not sure how to get the end position at all