Backport PR #16742: nbagg: Don't send events if manager is disconnected.

jklymak · meeseeksmachine · commit f13974d514b7 · 2020-03-12T16:26:42.000Z
diff --git a/lib/matplotlib/backends/backend_webagg_core.py b/lib/matplotlib/backends/backend_webagg_core.py
@@ -343,7 +343,8 @@ def handle_set_dpi_ratio(self, event):
             self.draw_idle()
 
     def send_event(self, event_type, **kwargs):
-        self.manager._send_event(event_type, **kwargs)
+        if self.manager:
+            self.manager._send_event(event_type, **kwargs)
 
 
 _JQUERY_ICON_CLASSES = {
