nbagg: Don't send events if manager is disconnected.

QuLogic · QuLogic · commit 36059d8656c5 · 2020-03-12T05:26:35.000-04:00
This occurs, e.g., when saving figures, as one of the first things `print_figure` does is to remove the figure manager. This does mean that nbagg won't be able to set the wait cursor when saving a file, but before 0944dcb that was not being done, and after, saving was broken, so there's no net loss. Fixes #16721.
diff --git a/lib/matplotlib/backends/backend_webagg_core.py b/lib/matplotlib/backends/backend_webagg_core.py
@@ -341,7 +341,8 @@ 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 = {
