### 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);
	const Ref<Texture2D> *tex = theme_icon_override.getptr(p_name);
	return tex != nullptr;
}
bool Window::has_theme_stylebox_override(const StringName &p_name) const {
	ERR_READ_THREAD_GUARD_V(false);
	const Ref<StyleBox> *style = theme_style_override.getptr(p_name);
	return style != nullptr;
}
bool Window::has_theme_font_override(const StringName &p_name) const {
	ERR_READ_THREAD_GUARD_V(false);
	const Ref<Font> *font = theme_font_override.getptr(p_name);
	return font != nullptr;
}
bool Window::has_theme_font_size_override(const StringName &p_name) const {
	ERR_READ_THREAD_GUARD_V(false);
	const int *font_size = theme_font_size_override.getptr(p_name);
	return font_size != nullptr;
}
bool Window::has_theme_color_override(const StringName &p_name) const {
	ERR_READ_THREAD_GUARD_V(false);
	const Color *color = theme_color_override.getptr(p_name);
	return color != nullptr;
}
bool Window::has_theme_constant_override(const StringName &p_name) const {
	ERR_READ_THREAD_GUARD_V(false);
	const int *constant = theme_constant_override.getptr(p_name);
	return constant != nullptr;
}
float Window::get_theme_default_base_scale() const {