No warning with wxUSE_BUSYINFO turned off.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@27750 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/html/helpctrl.cpp

@@ -111,6 +111,8 @@ bool wxHtmlHelpController::AddBook(const wxString& book, bool show_wait_msg)
 #if wxUSE_BUSYINFO
     if (show_wait_msg)
         delete busy;
+#else
+    wxUnusedVar(show_wait_msg);
 #endif
     if (m_helpFrame) 
         m_helpFrame->RefreshLists();