Fix infinite loop in AdtsExtractor sniffing malformed or non-ADTS streams.

Here is a WAV that exhibits this issue:
https://storage.googleapis.com/courtside-public/dcower/reaper_16bit_nonbwf.wav
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=120334203

library/src/main/java/com/google/android/exoplayer/extractor/ts/AdtsExtractor.java

@@ -102,6 +102,10 @@ public final class AdtsExtractor implements Extractor {
         input.peekFully(scratch.data, 0, 4);
         scratchBits.setPosition(14);
         int frameSize = scratchBits.readBits(13);
+        // Either the stream is malformed OR we're not parsing an ADTS stream.
+        if (frameSize <= 6) {
+          return false;
+        }
         input.advancePeekPosition(frameSize - 6);
         validFramesSize += frameSize;
       }