hellp: show all valid help items also in the Write-Out menu

Subtract one from the count only if all possible items in the menu
have been counted (item == NULL), meaning that the last item in the
Write-Out menu (the 'discard_buffer' function) has been counted too.

This fixes https://savannah.gnu.org/bugs/?59549.

Bug existed since version 4.5, commit b3ace4d8.

src/global.c

@@ -477,7 +477,8 @@ size_t shown_entries_for(int menu)
 	}
 
 	/* When --saveonexit is not used, widen the grid of the WriteOut menu. */
-	if (menu == MWRITEFILE && first_sc_for(menu, discard_buffer) == NULL)
+	if (menu == MWRITEFILE && item == NULL &&
+						first_sc_for(menu, discard_buffer) == NULL)
 		count--;
 
 	return count;