http://bugs.winehq.org/show_bug.cgi?id=16466
--- Comment #13 from Mikolaj Zalewski mikolaj.zalewski@gmail.com 2009-01-12 14:59:51 --- Thank you for working on this bug. But are you sure a NULL should mean a callback item? It would be logical if it cleared the string (but, of course, there is no guarantee Windows APIs are logical). The best solution would be to write a testcase for this in dlls/comctl32/tests/toolbar.c.