Fix error reporting

Interpolate types so the modules don't need to be imported
add MethodError case

Author: contradict

src/systems/model_parsing.jl

@@ -639,8 +639,10 @@ function parse_variable_arg(dict, mod, arg, varclass, kwargs, where_types)
                 try
                     $setdefault($vv, $convert_units($unit, $name))
                 catch e
-                    if isa(e, DynamicQuantities.DimensionError) || isa(e, Unitful.DimensionError)
+                    if isa(e, $(DynamicQuantities.DimensionError)) || isa(e, $(Unitful.DimensionError))
                         error("Unable to convert units for \'"*string(:($$vv))*"\'")
+                    elseif isa(e, MethodError)
+                        error("No or invalid units provided for \'"*string(:($$vv))*"\'")
                     else
                         rethrow(e)
                     end