### 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
se->connect("edited_script_changed", callable_mp(this, &ScriptEditor::_script_changed));
	se->connect("request_help", callable_mp(this, &ScriptEditor::_help_search));
	se->connect("request_open_script_at_line", callable_mp(this, &ScriptEditor::_goto_script_line));
	se->connect("go_to_help", callable_mp(this, &ScriptEditor::_help_class_goto));
	se->connect("request_save_history", callable_mp(this, &ScriptEditor::_save_history));
	se->connect("search_in_files_requested", callable_mp(this, &ScriptEditor::_on_find_in_files_requested));
	se->connect("replace_in_files_requested", callable_mp(this, &ScriptEditor::_on_replace_in_files_requested));
	se->connect("go_to_method", callable_mp(this, &ScriptEditor::script_goto_method));
	
	_test_script_times_on_disk(p_resource);
	_update_modified_scripts_for_external_editor(p_resource);
	if (p_line > 0) {
		se->goto_line(p_line - 1);
	}
	notify_script_changed(p_resource);
	return true;
}
void ScriptEditor::save_current_script() {
	ScriptEditorBase *current = _get_current_editor();
	if (!current || _test_script_times_on_disk()) {
		return;
	}
	if (trim_trailing_whitespace_on_save) {
		current->trim_trailing_whitespace();
	}
	current->insert_final_newline();
	if (convert_indent_on_save) {
		if (use_space_indentation) {
			current->convert_indent_to_spaces();
		} else {