Pamhyr: Implement window duplication deny mechanism with hash (#7).

src/View/CheckList/Window.py

@@ -68,6 +68,9 @@ class CheckListWindow(PamhyrWindow):
             parent=parent
         )
 
+        # Add solver to hash computation data
+        self._hash_data.append(self._solver)
+
         self._checker_list = (
             self._study.checkers() +
             self._solver.checkers()