### 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.
ERR_READ_THREAD_GUARD_V(false);
	String sname = p_name;
	if (!sname.begins_with("theme_override")) {
		return false;
	}
	if (sname.begins_with("theme_override_icons/")) {
		String name = sname.get_slicec('/', 1);
		r_ret = theme_icon_override.has(name) ? Variant(theme_icon_override[name]) : Variant();
	} else if (sname.begins_with("theme_override_styles/")) {
		String name = sname.get_slicec('/', 1);
		r_ret = theme_style_override.has(name) ? Variant(theme_style_override[name]) : Variant();
	} else if (sname.begins_with("theme_override_fonts/")) {
		String name = sname.get_slicec('/', 1);
		r_ret = theme_font_override.has(name) ? Variant(theme_font_override[name]) : Variant();
	} else if (sname.begins_with("theme_override_font_sizes/")) {
		String name = sname.get_slicec('/', 1);
		r_ret = theme_font_size_override.has(name) ? Variant(theme_font_size_override[name]) : Variant();
	} else if (sname.begins_with("theme_override_colors/")) {
		String name = sname.get_slicec('/', 1);
		r_ret = theme_color_override.has(name) ? Variant(theme_color_override[name]) : Variant();
	} else if (sname.begins_with("theme_override_constants/")) {
		String name = sname.get_slicec('/', 1);
		r_ret = theme_constant_override.has(name) ? Variant(theme_constant_override[name]) : Variant();
	} else {
		return false;
	}
	return true;
}
void Window::_get_property_list(List<PropertyInfo> *p_list) const {