Extension:Maps / chg - consistency
The second part of these two messages seems to be identical: Maps-error-no-layertype ("You need to specify the layer type. {{PLURAL:$2|Only this type is|These types are}} supported: $1") and Maps-error-invalid-layertype ("There are no layers of type "$1". Only {{PLURAL:$3|this type is|these types are}} supported: $2"). Why not adjusting them, except for the parameters of course.
kgh