### Godot version

4.1.dev (dc625bcbfc5b587ba8867481ee7a1f6a567c25d0)

### System information

Mageia 9, Linux

### Issue description

When importing a project in current `master`, the following error is raised for each asset that gets imported:
```
Attempting to parent and popup a dialog that already has a parent.
```

It seems to be raised once per asset, caused by the progress dialog.

CC @bruvzg

### Steps to reproduce

- Import a new project in Godot that contains importable assets, e.g. https://github.com/RPicster/godot4-demo-desert-light

### Minimal reproduction project

See above.
_THREAD_SAFE_METHOD_
	ERR_FAIL_COND_MSG(tasks.has(p_task), "Task '" + p_task + "' already exists.");
	BackgroundProgress::Task t;
	t.hb = memnew(HBoxContainer);
	Label *l = memnew(Label);
	l->set_text(p_label + " ");
	t.hb->add_child(l);
	t.progress = memnew(ProgressBar);
	t.progress->set_max(p_steps);
	t.progress->set_value(p_steps);
	Control *ec = memnew(Control);
	ec->set_h_size_flags(SIZE_EXPAND_FILL);
	ec->set_v_size_flags(SIZE_EXPAND_FILL);
	t.progress->set_anchors_and_offsets_preset(Control::PRESET_FULL_RECT);
	ec->add_child(t.progress);
	ec->set_custom_minimum_size(Size2(80, 5) * EDSCALE);
	t.hb->add_child(ec);
	add_child(t.hb);
	tasks[p_task] = t;
}
void BackgroundProgress::_update() {