patch 8.2.4028: ml_get error with :doautoall and Visual area

Problem:    ml_get error with :doautoall and Visual area. (Sean Dewar)
Solution:   Disable Visual mode while executing autocommands.
diff --git a/src/structs.h b/src/structs.h
index 197df72..9d57681 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -4031,6 +4031,7 @@
     int		save_prevwin_id;    // ID of saved prevwin
     bufref_T	new_curbuf;	    // new curbuf
     char_u	*globaldir;	    // saved value of globaldir
+    int		save_VIsual_active; // saved VIsual_active
 } aco_save_T;
 
 /*