### Godot version

4.1

### System information

Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1060 (NVIDIA; 30.0.15.1403) - Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz (8 Threads)

### Issue description


https://github.com/godotengine/godot/assets/2223172/3c8ee782-9d5f-42e3-a70f-d2aa59a233dd

We correctly clamp the size to 16x16 everywhere except here (probably).

### Steps to reproduce

1. Add a class with custom icon, e.g.
```GDScript
@icon("res://icon.svg")
extends Node
class_name Icon
```
2. Add it to scene
3. Open Script Editor and drag the node to script editor

### Minimal reproduction project

N/A
if (p_can_rename) {
		tree->set_allow_rmb_select(true);
		tree->connect("item_mouse_selected", callable_mp(this, &SceneTreeEditor::_rmb_select));
		tree->connect("empty_clicked", callable_mp(this, &SceneTreeEditor::_empty_clicked));
	}
	tree->connect("cell_selected", callable_mp(this, &SceneTreeEditor::_selected_changed));
	tree->connect("item_edited", callable_mp(this, &SceneTreeEditor::_renamed));
	tree->connect("multi_selected", callable_mp(this, &SceneTreeEditor::_cell_multi_selected));
	tree->connect("button_clicked", callable_mp(this, &SceneTreeEditor::_cell_button_pressed));
	tree->connect("nothing_selected", callable_mp(this, &SceneTreeEditor::_deselect_items));
	error = memnew(AcceptDialog);
	add_child(error);
	warning = memnew(AcceptDialog);
	add_child(warning);
	warning->set_title(TTR("Node Configuration Warning!"));
	last_hash = 0;
	blocked = 0;
	update_timer = memnew(Timer);
	update_timer->connect("timeout", callable_mp(this, &SceneTreeEditor::_update_tree).bind(false));
	update_timer->set_one_shot(true);
	update_timer->set_wait_time(0.5);
	add_child(update_timer);
	script_types = memnew(List<StringName>);
	ClassDB::get_inheriters_from_class("Script", script_types);
}
SceneTreeEditor::~SceneTreeEditor() {
	memdelete(script_types);
}
/******** DIALOG *********/
void SceneTreeDialog::popup_scenetree_dialog() {