NuPlayerDecoder: check mCodec before dereferencing it.

Test: media cts tests
Bug: 37538141
Change-Id: Ib95fd4786242d6742f3bdc7aab28f79d43e8da81
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayerDecoder.cpp b/media/libmediaplayerservice/nuplayer/NuPlayerDecoder.cpp
index 9e579f9..a4a5861 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayerDecoder.cpp
+++ b/media/libmediaplayerservice/nuplayer/NuPlayerDecoder.cpp
@@ -95,7 +95,11 @@
 }
 
 NuPlayer::Decoder::~Decoder() {
-    mCodec->release();
+    // Need to stop looper first since mCodec could be accessed on the mDecoderLooper.
+    stopLooper();
+    if (mCodec != NULL) {
+        mCodec->release();
+    }
     releaseAndResetMediaBuffers();
 }