When using wxPGEditor_Choice colour property, cancelling the choice of the custom colour reset the previously selected custom colour. Fix this by correcting the test for the custom colour which didn't work before. Closes #15542. git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@76627 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775