bottombar: only count help items that have a shortcut bound to them

This avoids showing a ghost item in, for example, the WriteOut menu
when not using --tempfile and the user does not bind 'discardbuffer'.

src/global.c

@@ -230,9 +230,9 @@ size_t length_of_list(int menu)
     size_t i = 0;
 
     for (f = allfuncs; f != NULL; f = f->next)
-	if ((f->menus & menu) != 0) {
+	if ((f->menus & menu) && first_sc_for(menu, f->scfunc) != NULL)
 	    i++;
-	}
+
     return i;
 }