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
diff --git a/libs/hwui/jni/NinePatch.cpp b/libs/hwui/jni/NinePatch.cpp
index 6942017..3ca457f 100644
--- a/libs/hwui/jni/NinePatch.cpp
+++ b/libs/hwui/jni/NinePatch.cpp
@@ -67,7 +67,7 @@
         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];