### Godot version

3.5.1mono

### System information

windows10

### Issue description

Error message
 scene/main/node.cpp:1362 - Index p_index = 0 is out of bounds (data.children.size() = 0).
 scene/main/node.cpp:397 - Parameter "p_child" is null.
 scene/gui/tab_container.cpp:593 - Index p_current = 0 is out of bounds (get_tab_count() = 0).
See "Steps to reproduce for details"

### Steps to reproduce

Set an external text editor
Create a script
Drop the script to the built-in text editor like this image:
![image](https://user-images.githubusercontent.com/119792950/209504041-039f2620-5e42-4c0f-8c41-cd24486fb3d2.png)
And got error message:
 scene/main/node.cpp:1362 - Index p_index = 0 is out of bounds (data.children.size() = 0).
 scene/main/node.cpp:397 - Parameter "p_child" is null.
 scene/gui/tab_container.cpp:593 - Index p_current = 0 is out of bounds (get_tab_count() = 0).

### Minimal reproduction project

An empty project
script_list->set_item_icon_modulate(-1, tool_color);
		}
		int index = script_list->get_item_count() - 1;
		script_list->set_item_tooltip(index, sedata_filtered[i].tooltip);
		script_list->set_item_metadata(index, sedata_filtered[i].index); 
		if (sedata_filtered[i].used) {
			script_list->set_item_custom_bg_color(index, Color(88 / 255.0, 88 / 255.0, 60 / 255.0));
		}
		if (tab_container->get_current_tab() == sedata_filtered[i].index) {
			script_list->select(index);
			script_name_label->set_text(sedata_filtered[i].name);
			script_icon->set_texture(sedata_filtered[i].icon);
			ScriptEditorBase *se = _get_current_editor();
			if (se) {
				se->enable_editor(this);
				_update_selected_editor_menu();
			}
		}
	}
	if (!waiting_update_names) {
		_update_members_overview();
		_update_help_overview();
	} else {
		waiting_update_names = false;
	}
	_update_members_overview_visibility();
	_update_help_overview_visibility();
	_update_script_colors();
}
Ref<TextFile> ScriptEditor::_load_text_file(const String &p_path, Error *r_error) const {