Modify error handling for missing video m-lines and local description (#632)

* ref(sdp): lower logs about missing local video to warning

* ref(sdp): earlier error handling for missing description and mlines

* ref(sdp): rename maybeMungeLocalSdp to be more specific

modules/RTC/LocalSdpMunger.js

         const videoMLine = transformer.selectMedia('video');
 
         if (!videoMLine) {
-            logger.error(
+            logger.debug(
                 `${this.tpc} unable to hack local video track SDP`
                     + '- no "video" media');
 
      *
      * @param {object} desc the WebRTC SDP object instance for the local
      * description.
+     * @returns {RTCSessionDescription}
      */
-    maybeMungeLocalSdp(desc) {
+    maybeAddMutedLocalVideoTracksToSDP(desc) {
         if (!desc || !(desc instanceof RTCSessionDescription)) {
             throw new Error('Incorrect type, expected RTCSessionDescription');
         }

modules/RTC/TraceablePeerConnection.js

     localDescription() {
         let desc = this.peerconnection.localDescription;
 
+        if (!desc) {
+            logger.debug('getLocalDescription no localDescription found');
+
+            return {};
+        }
+
         this.trace('getLocalDescription::preTransform', dumpSDP(desc));
 
         // if we're running on FF, transform to Plan B first.
-        if (desc && RTCBrowserType.usesUnifiedPlan()) {
+        if (RTCBrowserType.usesUnifiedPlan()) {
             desc = this.interop.toPlanB(desc);
             this.trace('getLocalDescription::postTransform (Plan B)',
                 dumpSDP(desc));
         }
 
         if (RTCBrowserType.doesVideoMuteByStreamRemove()) {
-            desc = this.localSdpMunger.maybeMungeLocalSdp(desc);
+            desc = this.localSdpMunger.maybeAddMutedLocalVideoTracksToSDP(desc);
             logger.debug(
                 'getLocalDescription::postTransform (munge local SDP)', desc);
         }
         // happening (check setLocalDescription impl).
         desc = enforceSendRecv(desc);
 
-        return desc || {};
+        return desc;
     },
     remoteDescription() {
         let desc = this.peerconnection.remoteDescription;

modules/xmpp/RtxModifier.js

         const videoMLine = sdpTransformer.selectMedia('video');
 
         if (!videoMLine) {
-            logger.error(`No 'video' media found in the sdp: ${sdpStr}`);
+            logger.debug(`No 'video' media found in the sdp: ${sdpStr}`);
 
             return sdpStr;
         }
         const videoMLine = sdpTransformer.selectMedia('video');
 
         if (!videoMLine) {
-            logger.error(`No 'video' media found in the sdp: ${sdpStr}`);
+            logger.debug(`No 'video' media found in the sdp: ${sdpStr}`);
 
             return sdpStr;
         }

modules/xmpp/SDPUtil.js

     preferVideoCodec(videoMLine, codecName) {
         let payloadType = null;
 
-        if (!codecName) {
+        if (!videoMLine || !codecName) {
             return;
         }
 
      * @param {string} codecName the name of the codec which will be stripped.
      */
     stripVideoCodec(videoMLine, codecName) {
-        if (!codecName) {
+        if (!videoMLine || !codecName) {
             return;
         }
 

modules/xmpp/SdpConsistency.js

         const videoMLine = sdpTransformer.selectMedia('video');
 
         if (!videoMLine) {
-            logger.error(
+            logger.debug(
                 `${this.logPrefix} no 'video' media found in the sdp: `
                     + `${sdpStr}`);