fix: error if container_type passed to MTKParameters is not an AbstractArray subtype

Author: AayushSabharwal

src/systems/parameter_buffer.jl

@@ -31,7 +31,10 @@ function MTKParameters(
         t0 = nothing, substitution_limit = 1000, floatT = nothing,
         container_type = Vector)
     if !(container_type <: AbstractArray)
-        container_type = Array
+        throw(ArgumentError("""
+        `container_type` for `MTKParameters` must be a subtype of `AbstractArray`. Found \
+        $container_type.
+        """))
     end
     ic = if has_index_cache(sys) && get_index_cache(sys) !== nothing
         get_index_cache(sys)

src/systems/problem_utils.jl

@@ -1150,6 +1150,10 @@ function process_SciMLProblem(
     end
     evaluate_varmap!(op, ps; limit = substitution_limit)
     if is_split(sys)
+        # `pType` is usually `Dict` when the user passes key-value pairs.
+        if !(pType <: AbstractArray)
+            pType = Array
+        end
         p = MTKParameters(sys, op; floatT = floatT, container_type = pType)
     else
         p = better_varmap_to_vars(op, ps; tofloat, container_type = pType)