Query about SDP manipulation

Greetings; I create this HMR rule for SDP manipulation which does following;

1. Check for altc2 header and if present modify the "c" and "m" line with the content of altc header

2.  altc can be either IPv4 or IPv6

3. The problem I am having is if their is an INVITE arrive without altc header, the HMR is deleting IP address from "c" line & "port from "m" line. Any idea how can I modify the HMR so that it can only applied if altc header is present and doesn't apply if altc header is not in the INVITE

name                                    useAltc2Media

        description