Enable Apply button to change internal state

When simulating it is now possible to change the system internal state
(any DCL-declared variable). The undo and redo buttons are active to
restore any state.

asn1_value_editor/sdlHandler.py

@@ -272,6 +272,7 @@ class sdlHandler(QObject):
         # Apply the change and create Undo command to restore previous state
         old_state = self.current_hash
         self.restore_global_state(new_hash)
+        self.current_hash = new_hash
         undo_cmd = SendTC(self, old_state)
         self.undo_stack.push(undo_cmd)