Even after the changes of r70415, we could still report an error when the
item client data was set to -1 (== CB_ERR) as checking for GetLastError() was
not enough, we need to also ensure that the last error is reset before trying
to get the client data.
Also apply the same fix to wxListBox and add the tests verifying that this
does work correctly.
Closes#13883.
Also fix wxListBox::GetClientData().
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74994 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
9d7f0c5f7e