### 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
highlighter->set_text_edit(text_edit);
	highlighter->clear_keyword_colors();
	highlighter->clear_member_keyword_colors();
	highlighter->clear_color_regions();
	highlighter->set_symbol_color(EDITOR_GET("text_editor/theme/highlighting/symbol_color"));
	highlighter->set_function_color(EDITOR_GET("text_editor/theme/highlighting/function_color"));
	highlighter->set_number_color(EDITOR_GET("text_editor/theme/highlighting/number_color"));
	highlighter->set_member_variable_color(EDITOR_GET("text_editor/theme/highlighting/member_variable_color"));
	
	const Color type_color = EDITOR_GET("text_editor/theme/highlighting/engine_type_color");
	List<StringName> types;
	ClassDB::get_class_list(&types);
	for (const StringName &E : types) {
		highlighter->add_keyword_color(E, type_color);
	}
	
	const Color usertype_color = EDITOR_GET("text_editor/theme/highlighting/user_type_color");
	List<StringName> global_classes;
	ScriptServer::get_global_class_list(&global_classes);
	for (const StringName &E : global_classes) {
		highlighter->add_keyword_color(E, usertype_color);
	}
	
	HashMap<StringName, ProjectSettings::AutoloadInfo> autoloads = ProjectSettings::get_singleton()->get_autoload_list();
	for (const KeyValue<StringName, ProjectSettings::AutoloadInfo> &E : autoloads) {
		const ProjectSettings::AutoloadInfo &info = E.value;
		if (info.is_singleton) {
			highlighter->add_keyword_color(info.name, usertype_color);