klippy: Only set the run_result if it hasn't already been set

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/klippy.py

@@ -202,7 +202,8 @@ class Printer:
     def send_event(self, event, *params):
         return [cb(*params) for cb in self.event_handlers.get(event, [])]
     def request_exit(self, result):
-        self.run_result = result
+        if self.run_result is None:
+            self.run_result = result
         self.reactor.end()