error: returning reference to local temporary object

I'm trying to connect the `animation_finished` event as follow:

```
void Hero::_register_methods() {
//....
register_method("_ready", &Hero::_ready);
register_method("AnimationFinished", &Hero::AnimationFinished);
}

void Hero::_ready() {
m_anim_player = get_node("Body/Skeleton/AnimationPlayer");

m_anim_player->connect("animation_finished", this, "AnimationFinished");
}

void Hero::AnimationFinished(const String& animation) {

}
```

but I get this error:

```
build/darwin/_deps/godot-cpp-src/include/core/Godot.hpp:163:10: error: returning reference to local temporary object [-Werror,-Wreturn-stack-address]
return a;
```

```
template
struct _ArgCast {
static T _arg_cast(Variant a) {
>>> return a;
}
};
```

however if I made the method accept normal String not by reference , it works fine
` void Hero::AnimationFinished( String animation) {}`

but isn't that unnecessary copying the parameters on each call?