[Bug 48815] user32:win "unexpected 0x738 message" Windows 10 failures

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=48815

--- Comment #1 from François Gouget  ---
Created attachment 70312
  --> https://bugs.winehq.org/attachment.cgi?id=70312
user32:win Dump the 0x738 messages

The attached patch confirms that the 0x738 message is sent to a message-only
UserAdapterWindowClass window:

win.c:4049: Test failed: message 0738 available
win.c:55: hwnd=00000000000301C0 pid=5144 tid=6984 now=68609
win.c:56: hwnd=00000000000201BA message=0738 wParam=0 lParam=0 time=68593
pt=(250,250)
win.c:60: wnd: parent=0000000000000000 owner=0000000000000000
win.c:65: wnd: pid=5144 tid=6984 class=22 L"UserAdapterWindowClass" text=0 L""
win.c:72: hwnd=00000000000201BA is a message-only window