Bug 1211956: Check result of EmptyShape::getInitialShape; r=h4writer

--HG--
extra : rebase_source : c2ec5ca1e09c8c5919a51469218bf58c070a8c54

js/src/vm/Shape.cpp

@@ -627,6 +627,9 @@ js::ReshapeForAllocKind(JSContext* cx, Shape* shape, TaggedProto proto,
     RootedId id(cx);
     RootedShape newShape(cx, EmptyShape::getInitialShape(cx, shape->getObjectClass(),
                                                          proto, nfixed, shape->getObjectFlags()));
+    if (!newShape)
+        return nullptr;
+
     for (unsigned i = 0; i < ids.length(); i++) {
         id = ids[i];