Code optimizations / refactor (#12704)

Co-authored-by: SmallJoker <SmallJoker@users.noreply.github.com>
Co-authored-by: sfan5 <sfan5@live.de>

src/script/lua_api/l_client.cpp

@@ -237,7 +237,7 @@ int ModApiClient::l_get_language(lua_State *L)
 #endif
 	std::string lang = gettext("LANG_CODE");
 	if (lang == "LANG_CODE")
-		lang = "";
+		lang.clear();
 
 	lua_pushstring(L, locale);
 	lua_pushstring(L, lang.c_str());