### 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
}
		if (!match(GDScriptTokenizer::Token::IDENTIFIER)) {
			break;
		}
		function = parse_identifier();
	}
	complete_extents(p_variable);
	if (p_variable->property == VariableNode::PROP_SETGET) {
		end_statement("property declaration");
	}
	if (p_need_indent) {
		consume(GDScriptTokenizer::Token::DEDENT, R"(Expected end of indented block for property.)");
	}
	return property;
}
void GDScriptParser::parse_property_setter(VariableNode *p_variable) {
	switch (p_variable->property) {
		case VariableNode::PROP_INLINE: {
			FunctionNode *function = alloc_node<FunctionNode>();
			IdentifierNode *identifier = alloc_node<IdentifierNode>();
			complete_extents(identifier);
			identifier->name = "@" + p_variable->identifier->name + "_setter";
			function->identifier = identifier;
			function->is_static = p_variable->is_static;
			consume(GDScriptTokenizer::Token::PARENTHESIS_OPEN, R"(Expected "(" after "set".)");
			ParameterNode *parameter = alloc_node<ParameterNode>();
			if (consume(GDScriptTokenizer::Token::IDENTIFIER, R"(Expected parameter name after "(".)")) {
				reset_extents(parameter, previous);
				p_variable->setter_parameter = parse_identifier();
				parameter->identifier = p_variable->setter_parameter;