don't filter empty u0maps

Author: ChrisRackauckas

src/systems/nonlinear/initializesystem.jl

@@ -27,7 +27,8 @@ function generate_initializesystem(sys::ODESystem;
         guessmap = [x[2] => get(guesses, x[1], default_dd_value)
                     for x in schedule.dummy_sub]
         dd_guess = Dict(filter(x -> !isnothing(x[1]), guessmap))
-        filtered_u0 = todict([get(schedule.dummy_sub, x[1], x[1]) => x[2] for x in u0map])
+        filtered_u0 = u0map === nothing || isempty(u0map) ? u0map :
+                      todict([get(schedule.dummy_sub, x[1], x[1]) => x[2] for x in u0map])
     else
         dd_guess = Dict()
         filtered_u0 = u0map