Fix -DLUA=OFF build on color radios (#21)

radio/src/gui/colorlcd/CMakeLists.txt

@@ -64,7 +64,6 @@ set(GUI_SRC
   menu_screen.cpp
   screen_setup.cpp
   switch_warn_dialog.cpp
-  standalone_lua.cpp
   )
 
 macro(add_gui_src src)
@@ -74,6 +73,10 @@ macro(add_gui_src src)
     )
 endmacro(add_gui_src)
 
+if(LUA)
+  add_gui_src(standalone_lua.cpp)
+endif()
+
 if(HELI)
   add_gui_src(model_heli.cpp)
 endif()