Correct bug of modifying self rather than self.local_group when text is blank

Author: kmatch98

adafruit_display_text/bitmap_label.py

@@ -228,9 +228,9 @@ def _reset_text(
                 0,  # zero width with text == ""
                 0,  # zero height with text == ""
             )
-            # Clear out any items in the self Group, in case this is an update to the bitmap_label
-            for _ in self:
-                self.pop(0)
+            # Clear out any items in the self.local_group Group, in case this is an update to the bitmap_label
+            for _ in self.local_group:
+                self.local_group.pop(0)
 
         else:  # The text string is not empty, so create the Bitmap and TileGrid and
             # append to the self Group