Fix compiler warnings in frameworks/av/media/ndk.

Bug: 26936282
Change-Id: I86b32ef5a7e6b18974cbe4a885291acec2b2eb5f
diff --git a/media/ndk/NdkMediaCodec.cpp b/media/ndk/NdkMediaCodec.cpp
index 5bb2dcd..2cb7cc7 100644
--- a/media/ndk/NdkMediaCodec.cpp
+++ b/media/ndk/NdkMediaCodec.cpp
@@ -145,10 +145,14 @@
     AMediaCodec *mData = new AMediaCodec();
     mData->mLooper = new ALooper;
     mData->mLooper->setName("NDK MediaCodec_looper");
-    status_t ret = mData->mLooper->start(
+    size_t res = mData->mLooper->start(
             false,      // runOnCallingThread
             true,       // canCallJava XXX
             PRIORITY_FOREGROUND);
+    if (res != OK) {
+        ALOGE("Failed to start the looper");
+        return NULL;
+    }
     if (name_is_type) {
         mData->mCodec = android::MediaCodec::CreateByType(mData->mLooper, name, encoder);
     } else {