Avoid randomizing SDP session version at zero

Zero is a valid version for new sessions (mentioned in RFC 2327) and still used by some SIP implementations.

(cherry picked from commit 78f9811fda)

daemon/sdp.c

@@ -2680,7 +2680,7 @@ int sdp_replace(struct sdp_chopper *chop, GQueue *sessions, struct call_monologu
 		session->origin.version_output_pos = chop->output->len;
 		if (!monologue->sdp_version) {
 			monologue->sdp_version = session->origin.version_num;
-			if (monologue->sdp_version == 0 || monologue->sdp_version == ULLONG_MAX)
+			if (monologue->sdp_version == ULLONG_MAX)
 				monologue->sdp_version = (unsigned int)ssl_random();
 		}