Catch error when shutting down kernel from the control channel

Author: ccordoba12

ipykernel/eventloops.py

@@ -285,7 +285,10 @@ def start(self):
 
 @loop_tk.exit
 def loop_tk_exit(kernel):
-    kernel.app_wrapper.app.destroy()
+    try:
+        kernel.app_wrapper.app.destroy()
+    except RuntimeError:
+        pass
 
 
 @register_integration('gtk')