fix(AvgRTPStatsReporter): do not print error

If the current browser does not support given stat no error should be
printed.

modules/RTC/RTCBrowserType.js

         return RTCBrowserType.isFirefox();
     },
 
+    /**
+     * Checks if the current browser reports upload and download bandwidth
+     * statistics.
+     * @return {boolean}
+     */
+    supportsBandwidthStatistics() {
+        // FIXME bandwidth stats are currently not implemented for FF on our
+        // side, but not sure if not possible ?
+        return !RTCBrowserType.isFirefox();
+    },
+
     /**
      * Whether jitsi-meet supports simulcast on the current browser.
      * @returns {boolean}

modules/statistics/AvgRTPStatsReporter.js

 import * as ConnectionQualityEvents
     from '../../service/connectivity/ConnectionQualityEvents';
 import * as ConferenceEvents from '../../JitsiConferenceEvents';
+import RTCBrowserType from '../RTC/RTCBrowserType';
 import Statistics from './statistics';
 
 const logger = getLogger(__filename);
     addNext(nextValue) {
         if (typeof nextValue !== 'number') {
             logger.error(
-                `${this.name} - invalid value for idx: ${this.count}`);
+                `${this.name} - invalid value for idx: ${this.count}`,
+                nextValue);
 
             return;
         }
 
         this._avgBitrateUp.addNext(bitrate.upload);
         this._avgBitrateDown.addNext(bitrate.download);
-        this._avgBandwidthUp.addNext(bandwidth.upload);
-        this._avgBandwidthDown.addNext(bandwidth.download);
+
+        if (RTCBrowserType.supportsBandwidthStatistics()) {
+            this._avgBandwidthUp.addNext(bandwidth.upload);
+            this._avgBandwidthDown.addNext(bandwidth.download);
+        }
+
         this._avgPacketLossUp.addNext(packetLoss.upload);
         this._avgPacketLossDown.addNext(packetLoss.download);
         this._avgPacketLossTotal.addNext(packetLoss.total);
         if (this._sampleIdx >= this._n) {
             this._avgBitrateUp.report(isP2P);
             this._avgBitrateDown.report(isP2P);
-            this._avgBandwidthUp.report(isP2P);
-            this._avgBandwidthDown.report(isP2P);
+            if (RTCBrowserType.supportsBandwidthStatistics()) {
+                this._avgBandwidthUp.report(isP2P);
+                this._avgBandwidthDown.report(isP2P);
+            }
             this._avgPacketLossUp.report(isP2P);
             this._avgPacketLossDown.report(isP2P);
             this._avgPacketLossTotal.report(isP2P);