Added try..catch to avoid looped mozRTCSessionDescription undefined exceptions in Firefox (as occured in 43.0). Shouldn't do much havoc I guess.

core/main/client/lib/webrtcadapter.js

@@ -77,12 +77,17 @@ if (navigator.mozGetUserMedia) {
     return new mozRTCPeerConnection(pcConfig, pcConstraints);
   };
 
+  try {
     // The RTCSessionDescription object.
     window.RTCSessionDescription = mozRTCSessionDescription;
 
     // The RTCIceCandidate object.
     window.RTCIceCandidate = mozRTCIceCandidate;
 
+  }catch(err) {
+    
+  }
+
   // getUserMedia constraints shim.
   getUserMedia = (webrtcDetectedVersion < 38) ?
       function(c, onSuccess, onError) {