Invert sense of a test.

Bug 10907247

Change-Id: I0665cce648dd892db4cc59e82c325b376dad97dd
diff --git a/vm/native/java_lang_Class.cpp b/vm/native/java_lang_Class.cpp
index c307353..9b3b2f0 100644
--- a/vm/native/java_lang_Class.cpp
+++ b/vm/native/java_lang_Class.cpp
@@ -798,7 +798,7 @@
     // Check another thread didn't cache an object, if we've won install the object.
     ScopedPthreadMutexLock lock(&dvm_dex->modLock);
 
-    if (dvm_dex->dex_object != NULL) {
+    if (dvm_dex->dex_object == NULL) {
         dvm_dex->dex_object = env->NewGlobalRef(local_ref);
     }
     return dvm_dex->dex_object;