### Godot version

v4.2.dev.custom_build [c3b0a92c3]

### System information

Debian Linux X11 Xfce

### Issue description

In the following scene tree it is not possible to write anything in `LineEditB`.
![image](https://github.com/godotengine/godot/assets/6299227/ce5f696a-d86a-402f-98f7-6a762f15543e)

I would expect, that it is possible to focus `LineEditB` with a mouse click and write into it.

Regression from #58334

### Steps to reproduce

1. Load and run MRP
2. Mouse Click into the left LineEditB
3. Type Keyboard => No letters appear in the LineEditB

Variant:

1. Load and run MRP
2. Mouse Click into the right LineEditA
3. Mouse Click into the left LineEditB
4. Type Keyboard => Letters appear in LineEditA instead of LineEditB


### Minimal reproduction project

[BugKeyInputRouting.zip](https://github.com/godotengine/godot/files/11994804/BugKeyInputRouting.zip)

ERR_READ_THREAD_GUARD_V(Size2());
	return _get_size();
}
void SubViewport::set_size_2d_override(const Size2i &p_size) {
	ERR_MAIN_THREAD_GUARD;
	_set_size(_get_size(), p_size, true);
}
Size2i SubViewport::get_size_2d_override() const {
	ERR_READ_THREAD_GUARD_V(Size2i());
	return _get_size_2d_override();
}
void SubViewport::set_size_2d_override_stretch(bool p_enable) {
	ERR_MAIN_THREAD_GUARD;
	if (p_enable == size_2d_override_stretch) {
		return;
	}
	size_2d_override_stretch = p_enable;
	_set_size(_get_size(), _get_size_2d_override(), true);
}
bool SubViewport::is_size_2d_override_stretch_enabled() const {