correctly check inaxes for multicursor

Author: ianhi

lib/matplotlib/widgets.py

@@ -1653,7 +1653,7 @@ def clear(self, event):
     def onmove(self, event):
         if self.ignore(event):
             return
-        if event.inaxes is None:
+        if event.inaxes not in self.axes:
             return
         if not self.canvas.widgetlock.available(self):
             return