add error message if grid coords length !== n
add error message if grid coords length !== n

just in case.

agoldst/dfr-browser,joncgoodwin/dfr-browser,joncgoodwin/dfr-browser,agoldst/dfr-browser,altaf-ali/dfr-browser,joncgoodwin/dfr-browser,joncgoodwin/dfr-browser,altaf-ali/dfr-browser,agoldst/dfr-browser,joncgoodwin/dfr-browser,agoldst/dfr-browser,altaf-ali/dfr-browser,altaf-ali/dfr-browser