fixup! fix: allow passing nothing to override default for @mtkmodel models

Author: AayushSabharwal

src/systems/model_parsing.jl

@@ -169,8 +169,9 @@ function update_kwargs_and_metadata!(dict, kwargs, a, def, indices, type, var,
         push!(kwargs,
             Expr(:kw,
                 Expr(:(::), a,
-                    Expr(:curly, :Union, :Nothing, Expr(:curly, :AbstractArray, vartype))),
-                nothing))
+                    Expr(:curly, :Union, :Nothing, :Missing, NoValue,
+                        Expr(:curly, :AbstractArray, vartype))),
+                NO_VALUE))
         if !isnothing(meta) && haskey(meta, VariableUnit)
             push!(where_types, vartype)
         else

test/model_parsing.jl

@@ -840,7 +840,7 @@ end
             n[1:3] = if flag
                 [2, 2, 2]
             else
-                1
+                [1, 1, 1]
             end
         end
     end