Fix memory leak and abort

Release all pending buffers in case of error, don't just clear buffers.

Bug: 156819528
Test: fuzzer test case
Change-Id: If925a3b54cacf6cb9ce0e2092866caa68cc4b456
diff --git a/media/extractors/mkv/MatroskaExtractor.cpp b/media/extractors/mkv/MatroskaExtractor.cpp
index b88e4e8..27bd357 100644
--- a/media/extractors/mkv/MatroskaExtractor.cpp
+++ b/media/extractors/mkv/MatroskaExtractor.cpp
@@ -840,7 +840,7 @@
         }
 
         if (err != OK) {
-            mPendingFrames.clear();
+            clearPendingFrames();
 
             mBlockIter.advance();
             mbuf->release();