Unbreak NaCL build

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 01c0831b4ca5001950197e3931dc8a38a5d65889..3001972eef2ebd95b0754fb5f9578a00e9a8cf4d 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -6636,7 +6636,12 @@ MaybeHandle<Object> JSObject::DefineAccessor(Handle<JSObject> object,
   if (is_observed) {
     if (is_element) {
       Maybe<bool> maybe = HasOwnElement(object, index);
-      ASSERT(maybe.has_value);
+      // Workaround for a GCC 4.4.3 bug which leads to "‘preexists’ may be used
+      // uninitialized in this function".
+      if (!maybe.has_value) {
+        ASSERT(false);
+        return isolate->factory()->undefined_value();
+      }
       preexists = maybe.value;
       if (preexists && GetOwnElementAccessorPair(object, index).is_null()) {
         old_value =