fix: match cast type with declaration

Use the same target type as the declaration of the overload we call.
This compiles both with gcc and VS.

src/viacamcontroller.cpp

@@ -229,7 +229,7 @@ CCamera* CViacamController::SetUpCamera()
 
 			wxSingleChoiceDialog choiceDlg(
 				NULL, _("Choose the camera to use"), _T("Enable Viacam"), strArray, 
-				(char**)NULL, wxDEFAULT_DIALOG_STYLE | wxOK | wxCANCEL | wxCENTRE);
+				(void**)NULL, wxDEFAULT_DIALOG_STYLE | wxOK | wxCANCEL | wxCENTRE);
 
 			if (choiceDlg.ShowModal ()!= wxID_OK) return NULL;