From a client we receive an UPDATE message which contains the below media with fmt properties as below.
m=video 0 RTP/SAVP 0
Their aim is to close video media but it is causing us problems. Is their message correct?
The usual format of closing video stream which we can correctly handle is
m=video 0 RTP/AVP 96 97 98
This is correct. According to the RFC 3264:
Existing media streams are removed by creating a new SDP with the port number for that stream set to zero. The stream description MAY omit all attributes present previously, and MAY list just a single media format.
This makes sense, because when a participant doesn't want to have a video stream, it doesn't matter which formats it would be willing to use. m=video 0 RTP/SAVP 0 simply means "no video stream" or "terminate the video stream".
And there is no obligation that the media format in this case should make any sense. Just like in the message you received: the format 0 stands for PCMU, which is not even a video format.