Accept undecoded frame pairs in VideoLayerAnalyzer

Bug: webrtc:9883
Change-Id: I651bf21ebbf547389b36df077f6ff619c5e670b6
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/168043
Reviewed-by: Ali Tofigh <alito@webrtc.org>
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30442}

test/scenario/stats_collection.cc

@@ -99,7 +99,8 @@ void VideoLayerAnalyzer::HandleFramePair(VideoFramePair sample,
                    sample.capture_time.seconds<double>(),
                    sample.render_time.seconds<double>(),
                    sample.captured->width(), sample.captured->height(),
-                   sample.decoded->width(), sample.decoded->height(), psnr);
+                   sample.decoded ? sample.decoded->width() : 0,
+                   sample.decoded ? sample.decoded->height() : 0, psnr);
   }
 }