Merge pull request kivy#2349 from kived/textinput-win

ensure _win is set when updating graphics

Author: akshayaurora

kivy/uix/textinput.py

@@ -1121,6 +1121,9 @@ def _position_handles(self, *args, **kwargs):
         group = self.canvas.get_group('selection')
         if not group:
             return
+
+        if not self._win:
+            self._set_window()
         self._win.remove_widget(self._handle_middle)
 
         handle_left = self._handle_left