add missing utils fix

Author: ChrisRackauckas

src/utils.jl

@@ -271,13 +271,13 @@ function lower_varname(t::Term, iv)
 end
 lower_varname(t::Sym, iv) = t
 
-function lower_mapnames(umap::AbstractArray{<:Pair{Symbol,T}},name::Nothing=nothing) where T
+function lower_mapnames(umap::AbstractArray{<:Pair{Symbol,T}}) where T
     [value(k) => value(v) for (k, v) in umap]
 end
 function lower_mapnames(umap::AbstractArray{<:Pair{Symbol,T}},name) where T
     [lower_varname(value(k), name) => value(v) for (k, v) in umap]
 end
-lower_mapnames(umap::AbstractArray{<:Number},name::Nothing=nothing) = umap # Ambiguity
+lower_mapnames(umap::AbstractArray{<:Number}) = umap # Ambiguity
 lower_mapnames(umap::AbstractArray{<:Number},name) = umap
 
 function flatten_differential(O::Term)