### Godot version

v4.0.2.stable.custom_build (nixpkgs version)

### System information

NixOS

### Issue description

The [docs](https://docs.godotengine.org/en/latest/tutorials/scripting/gdscript/gdscript_basics.html#variables) seem to specify that uninitialized variables are null (as noted in this comment on the related issue: https://github.com/godotengine/godot/issues/56223#issuecomment-1175794500):
`var a # Data type is 'null' by default.`

This isn't always the case inside branches within loops. Instead, the variables can take on values from other branches.

### Related
- https://github.com/godotengine/godot/issues/56223

### Steps to reproduce

```
@tool
extends EditorScript

func _run():
	for i in 5:
		if i % 2:
			var j = i
			print("i = %s, j = %s" % [i, j])
		else:
			var k
			print("i = %s, k = %s" % [i, k])
```

Running this prints:
```
i = 0, k = <null>
i = 1, j = 1
i = 2, k = 1
i = 3, j = 3
i = 4, k = 3
```

This version also gives the exact same result:
```
@tool
extends EditorScript

func _run():
	for i in 5:
		match i % 2:
			1:
				var j = i
				print("i = %s, j = %s" % [i, j])
			0:
				var k
				print("i = %s, k = %s" % [i, k])
```

In addition, behavior similar to that described in https://github.com/godotengine/godot/issues/56223#issuecomment-1000996579 can still be reproduced as follows:
```
@tool
extends EditorScript

func _run():
	for i in 3:
		if i % 2:
			for j in range(1, 6, 3):
				pass
			print("i = %s" % i)
		else:
			var k
			var l
			var m
			print("i = %s, k = %s, l = %s, m = %s" % [i, k, l, m])
```
Which prints:
```
i = 0, k = <null>, l = <null>, m = <null>
i = 1
i = 2, k = 4, l = 7, m = (1, 6, 3)
```

### Minimal reproduction project

N/A
}
	parse_class_body(true);
	complete_extents(head);
#ifdef TOOLS_ENABLED
	for (const KeyValue<int, GDScriptTokenizer::CommentData> &E : tokenizer.get_comments()) {
		if (E.value.new_line && E.value.comment.begins_with("##")) {
			class_doc_line = MIN(class_doc_line, E.key);
		}
	}
	if (has_comment(class_doc_line)) {
		get_class_doc_comment(class_doc_line, head->doc_brief_description, head->doc_description, head->doc_tutorials, false);
	}
#endif 
	if (!check(GDScriptTokenizer::Token::TK_EOF)) {
		push_error("Expected end of file.");
	}
	clear_unused_annotations();
}
GDScriptParser::ClassNode *GDScriptParser::find_class(const String &p_qualified_name) const {
	String first = p_qualified_name.get_slice("::", 0);
	Vector<String> class_names;
	GDScriptParser::ClassNode *result = nullptr;
	
	if (first.is_empty() || (head->identifier && first == head->identifier->name)) {
		class_names = p_qualified_name.split("::");
		result = head;
	} else if (p_qualified_name.begins_with(script_path)) {
		
		class_names = p_qualified_name.trim_prefix(script_path).split("::");
		result = head;