ensure that media.candidates exists before stripping mDNS candidates

bigbluebutton-html5/imports/utils/sdpUtils.js

@@ -49,13 +49,15 @@ const stripMDnsCandidates = (sdp) => {
   const parsedSDP = transform.parse(sdp);
   let strippedCandidates = 0;
   parsedSDP.media.forEach((media) => {
-    media.candidates = media.candidates.filter((candidate) => {
-      if (candidate.ip && candidate.ip.indexOf('.local') === -1) {
-        return true;
-      }
-      strippedCandidates += 1;
-      return false;
-    });
+    if (media.candidates) {
+      media.candidates = media.candidates.filter((candidate) => {
+        if (candidate.ip && candidate.ip.indexOf('.local') === -1) {
+          return true;
+        }
+        strippedCandidates += 1;
+        return false;
+      });
+    }
   });
   if (strippedCandidates > 0) {
     logger.info({ logCode: 'sdp_utils_mdns_candidate_strip' }, `Stripped ${strippedCandidates} mDNS candidates`);