fix: optimization: PVS-Studio warning V821

Creating variables in a more localized scope can enhance performance and make the code easier to understand.

Reported by: PVS-Studio
Signed-off-by: Vyacheslav Ivanov <islavaivanov76@gmail.com>

src/logic/scripting/lua/libgui.cpp

@@ -324,8 +324,6 @@ static int l_gui_getattr(lua::State* L) {
     auto docname = lua::require_string(L, 1);
     auto element = lua::require_string(L, 2);
     auto attr = lua::require_string(L, 3);
-    auto docnode = getDocumentNode(L, docname, element);
-    auto node = docnode.node;
 
     static const std::unordered_map<std::string_view, std::function<int(UINode*,lua::State*)>> getters {
         {"color", p_get_color},
@@ -367,6 +365,8 @@ static int l_gui_getattr(lua::State* L) {
     };
     auto func = getters.find(attr);
     if (func != getters.end()) {
+        auto docnode = getDocumentNode(L, docname, element);
+        auto node = docnode.node;
         return func->second(node.get(), L);
     }
     return 0;