Set default keybinding when key does not exist.

- Fix #463

src/wx/opts.cpp

@@ -634,6 +634,7 @@ void load_opts()
     }
 
     // joypad is special
+    set_default_keys();
     for (int i = 0; i < 4; i++) {
         for (int j = 0; j < NUM_KEYS; j++) {
             wxString optname;