Fix background when using Selector, blitting and the background hasn't been created yet.

ericpre · ericpre · commit 031f77c1bf8a · 2021-05-19T16:16:34.000+01:00
diff --git a/lib/matplotlib/widgets.py b/lib/matplotlib/widgets.py
@@ -1782,6 +1782,8 @@ def update(self):
         if self.useblit:
             if self.background is not None:
                 self.canvas.restore_region(self.background)
+            else:
+                self.update_background(None)
             for artist in self.artists:
                 self.ax.draw_artist(artist)
             self.canvas.blit(self.ax.bbox)
