NuPlayerRenderer: prepareForMediaRenderingStart_l on en/disable offload audio

Bug: 22662910
Change-Id: I8fb4a9fce801295a4b251e27965aef048d217da6
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayer.cpp b/media/libmediaplayerservice/nuplayer/NuPlayer.cpp
index 8e3e460..bfdb1ad 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayer.cpp
+++ b/media/libmediaplayerservice/nuplayer/NuPlayer.cpp
@@ -1474,8 +1474,10 @@
         sp<AMessage> format = mSource->getFormat(true /*audio*/);
         tryOpenAudioSinkForOffload(format, hasVideo);
     } else {
-        mRenderer->signalDisableOffloadAudio();
-        mOffloadAudio = false;
+        if (mOffloadAudio) {
+            mRenderer->signalDisableOffloadAudio();
+            mOffloadAudio = false;
+        }
     }
 }