fix: null check firstKeyFrame in ts-inspector (#251)

Fixes #250

Author: cmacq2

lib/tools/ts-inspector.js

@@ -220,8 +220,24 @@ var parseVideoPes_ = function(bytes, pmt, result) {
                     i += pes.byteLength;
                   }
                   if (probe.ts.videoPacketContainsKeyFrame(frame)) {
-                    result.firstKeyFrame = probe.ts.parsePesTime(frame);
-                    result.firstKeyFrame.type = 'video';
+                    var firstKeyFrame = probe.ts.parsePesTime(frame);
+
+                    // PTS/DTS may not be available. Simply *not* setting
+                    // the keyframe seems to work fine with HLS playback
+                    // and definitely preferable to a crash with TypeError...
+                    if (firstKeyFrame) {
+                      result.firstKeyFrame = firstKeyFrame;
+                      result.firstKeyFrame.type = 'video';
+                    } else {
+                      // eslint-disable-next-line
+                      console.warn(
+                        'Failed to extract PTS/DTS from PES at first keyframe. ' +
+                        'This could be an unusual TS segment, or else mux.js did not ' +
+                        'parse your TS segment correctly. If you know your TS ' +
+                        'segments do contain PTS/DTS on keyframes please file a bug ' +
+                        'report! You can try ffprobe to double check for yourself.'
+                      );
+                    }
                   }
                   currentFrame.size = 0;
                 }