Bug 1128179 - Avoiding crash when appending data after decoder initialization failed. r=jya

--HG--
extra : rebase_source : 42d3c13c175cbe6a6e81bc56e3d61f596eae970f

dom/media/mediasource/TrackBuffer.cpp

@@ -168,7 +168,7 @@ TrackBuffer::AppendData(LargeDataBuffer* aData, int64_t aTimestampOffset)
         mLastEndTimestamp &&
         (!mParser->TimestampsFuzzyEqual(start, mLastEndTimestamp.value()) ||
          mLastTimestampOffset != aTimestampOffset ||
-         mDecoderPerSegment || mCurrentDecoder->WasTrimmed())) {
+         mDecoderPerSegment || (mCurrentDecoder && mCurrentDecoder->WasTrimmed()))) {
       MSE_DEBUG("TrackBuffer(%p)::AppendData: Data last=[%lld, %lld] overlaps [%lld, %lld]",
                 this, mLastStartTimestamp, mLastEndTimestamp.value(), start, end);