fix: use system guesses in initialization problem

Author: AayushSabharwal

src/systems/diffeqs/abstractodesystem.jl

@@ -1527,7 +1527,7 @@ function InitializationProblem{iip, specialize}(sys::AbstractODESystem,
         guesses = Dict()
     end
 
-    u0map = merge(todict(guesses), todict(u0map))
+    u0map = merge(ModelingToolkit.guesses(sys), todict(guesses), todict(u0map))
     if neqs == nunknown
         NonlinearProblem(isys, u0map, parammap; kwargs...)
     else