Return 0 instead of NULL for jlong

musl libc defines NULL as nullptr, which is explicitly allowed by
C++11.  nullptr_t cannot be implicitly cast to an integral type.
Return 0 instead.

Bug: 190084016
Test: m USE_HOST_MUSL=true host-native
Change-Id: Id83c1994a95cb105785c8ad902d2fe0589cb188d

libs/hwui/jni/NinePatch.cpp

@@ -67,7 +67,7 @@ public:
         size_t chunkSize = env->GetArrayLength(obj);
         if (chunkSize < (int) (sizeof(Res_png_9patch))) {
             jniThrowRuntimeException(env, "Array too small for chunk.");
-            return NULL;
+            return 0;
         }
 
         int8_t* storage = new int8_t[chunkSize];

libs/hwui/jni/android_util_PathParser.cpp

@@ -61,7 +61,7 @@ static jlong createPathDataFromStringPath(JNIEnv* env, jobject, jstring inputStr
     } else {
         delete pathData;
         doThrowIAE(env, result.failureMessage.c_str());
-        return NULL;
+        return 0;
     }
 }