As commented on the bug report, the patch will avoid compilation error. But it may create a False sense of an Advanced Feature.
IMHO, it would not be a good idea to keep that option enabled if wxRE_ADVANCED is not at all available during compilation. If an user tries to use advanced regex function with wxRE_ADVANCED set to 0, the function will not work appropriately and we may see another bug report reporting that the advanced regex function is not working properly.
This is my concern about the patch. I think, it'd be better if the advanced regex functions are #ifdef'ed.
Regards,
Biplab