Fix build.

Change-Id: Iaace063eaa65af842effa3e0b481a0629db58e42
diff --git a/core/jni/android_util_AssetManager.cpp b/core/jni/android_util_AssetManager.cpp
index 8a8b15f..785bf13 100644
--- a/core/jni/android_util_AssetManager.cpp
+++ b/core/jni/android_util_AssetManager.cpp
@@ -685,9 +685,9 @@
                                                            jobject outValue,
                                                            jboolean resolve)
 {
-    if (outValue == null) {
+    if (outValue == NULL) {
          jniThrowNullPointerException(env, "outValue");
-         return null;
+         return NULL;
     }
     AssetManager* am = assetManagerForJavaObject(env, clazz);
     if (am == NULL) {