fix: do not filter array unknowns in wrap_array_vars

Author: AayushSabharwal

src/systems/abstractsystem.jl

@@ -198,16 +198,10 @@ end
 
 function wrap_array_vars(sys::AbstractSystem, exprs; dvs = unknowns(sys))
     isscalar = !(exprs isa AbstractArray)
-    allvars = if isscalar
-        Set(get_variables(exprs))
-    else
-        union(get_variables.(exprs)...)
-    end
     array_vars = Dict{Any, AbstractArray{Int}}()
     for (j, x) in enumerate(dvs)
         if istree(x) && operation(x) == getindex
             arg = arguments(x)[1]
-            any(isequal(arg), allvars) || continue
             inds = get!(() -> Int[], array_vars, arg)
             push!(inds, j)
         end