Fix tests to pass with VerifyObject.

A SIRT ref with a null class was causing object verification problems
in space_test.

Change-Id: I95cfc3da5e0fec0155387f75612b0a3f26f6d3c9
diff --git a/runtime/jni_internal.cc b/runtime/jni_internal.cc
index f8865ea..6efff1a 100644
--- a/runtime/jni_internal.cc
+++ b/runtime/jni_internal.cc
@@ -3194,11 +3194,7 @@
   while (UNLIKELY(!allow_new_weak_globals_)) {
     weak_globals_add_condition_.WaitHoldingLocks(self);
   }
-  mirror::Object* obj = weak_globals_.Get(ref);
-  if (obj != kClearedJniWeakGlobal) {
-    VerifyObject(obj);
-  }
-  return obj;
+  return weak_globals_.Get(ref);
 }
 
 void JavaVMExt::DumpReferenceTables(std::ostream& os) {