guard against nodes deleted in collaborative session
guard against nodes deleted in collaborative session

mindmup/mapjs,mindmup/mapjs,danielrasmuson/mapjs,danielrasmuson/mapjs,AbdulMuhsinSE/mapjs,bhargav175/mapjs,bhargav175/mapjs,danielrasmuson/mapjs,AbdulMuhsinSE/mapjs,bhargav175/mapjs,pyxis777/mapjs,pyxis777/mapjs,AbdulMuhsinSE/mapjs,pyxis777/mapjs