more specific Problem.__getstate__ fix for starmap parallelization

Author: JoshKarpel

pymoo/model/problem.py

@@ -459,7 +459,12 @@ def calc_constraint_violation(G):
 
     def __getstate__(self):
         state = self.__dict__.copy()
-        state["parallelization"] = None
+
+        # If the parallelization is starmap,
+        # we can't pickle self with the starmapper function.
+        if state.get("parallelization", [None])[0] == "starmap":
+            state["parallelization"] = None
+
         return state
 
 # makes all the output at least 2-d dimensional