Added changes for building on Catalina

src/gui/update_checker.cpp

@@ -131,11 +131,15 @@ void check_updates() {
     check_updates_now();
   } else if (settings.check_updates == CHECK_IF_CONNECTED) {
     // only if internet connection exists
-    wxDialUpManager* dum = wxDialUpManager::Create();
+#if wxUSE_DIALUP_MANAGER
+	wxDialUpManager* dum = wxDialUpManager::Create();
     if (dum->IsOk() && dum->IsOnline()) {
       check_updates_now();
     }
     delete dum;
+#else
+	check_updates_now();
+#endif
   }
 }