Ensure resourceId mount option is not overwritten by the query string option (if the query string option is null/undefined)
Ensure resourceId mount option is not overwritten by the query string option (if the query string option is null/undefined)

Fixes #138

jumpinjackie/mapguide-react-layout,jumpinjackie/mapguide-react-layout,jumpinjackie/mapguide-react-layout,jumpinjackie/mapguide-react-layout,jumpinjackie/mapguide-react-layout