DNS Records allows to break zone

The DNS Records page allows to add an A and a CNAME record simultaneously for the same (sub)domain. However, Bind does not like this and refuses to load the zone afterwards, resulting in the slave DNS servers to forget the zone after the SOA limit, resulting in the domain being completely down. Virtualmin should check and dont't allow CNAME and A simultaneously. As far as I can see, such check is made if a CNAME is created when an A is existing. However, no check is made if a CNAME is existing and an A is added.