fix: only add Initial(D(x)) if iscall(x)

Author: AayushSabharwal

src/systems/abstractsystem.jl

@@ -720,7 +720,8 @@ function add_initialization_parameters(sys::AbstractSystem)
 
     # add derivatives of all variables for steady-state initial conditions
     if is_time_dependent(sys) && !(sys isa AbstractDiscreteSystem)
-        union!(all_initialvars, Differential(get_iv(sys)).(all_initialvars))
+        D = Differential(get_iv(sys))
+        union!(all_initialvars, [D(v) for v in all_initialvars if iscall(v)])
     end
     for eq in parameter_dependencies(sys)
         is_variable_floatingpoint(eq.lhs) || continue