### Godot version

3b086aa06

### System information

ArchLinux x11

### Issue description

```gdscript
extends Node

@export_group("My Properties")
@export var number = 3
@export var string = ""

@export_group("Prefixed Properties", "prefix_")
@export var prefix_number = 3
@export var prefix_string = ""

@export_group("", "")
@export var ungrouped_number = 3
```

![image](https://user-images.githubusercontent.com/70787919/214983963-528c415b-745b-47fc-9777-36ebe31a3060.png)


### Steps to reproduce

- create script
- @export_group
- go inspector

### Minimal reproduction project

‮
update_extents(assignment);
	make_completion_context(COMPLETION_ASSIGN, assignment);
#ifdef DEBUG_ENABLED
	bool has_operator = true;
#endif
	switch (previous.type) {
		case GDScriptTokenizer::Token::EQUAL:
			assignment->operation = AssignmentNode::OP_NONE;
			assignment->variant_op = Variant::OP_MAX;
#ifdef DEBUG_ENABLED
			has_operator = false;
#endif
			break;
		case GDScriptTokenizer::Token::PLUS_EQUAL:
			assignment->operation = AssignmentNode::OP_ADDITION;
			assignment->variant_op = Variant::OP_ADD;
			break;
		case GDScriptTokenizer::Token::MINUS_EQUAL:
			assignment->operation = AssignmentNode::OP_SUBTRACTION;
			assignment->variant_op = Variant::OP_SUBTRACT;
			break;
		case GDScriptTokenizer::Token::STAR_EQUAL:
			assignment->operation = AssignmentNode::OP_MULTIPLICATION;
			assignment->variant_op = Variant::OP_MULTIPLY;
			break;
		case GDScriptTokenizer::Token::STAR_STAR_EQUAL:
			assignment->operation = AssignmentNode::OP_POWER;
			assignment->variant_op = Variant::OP_POWER;
			break;
		case GDScriptTokenizer::Token::SLASH_EQUAL: