### 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
ParameterNode *parse_parameter();
	FunctionNode *parse_function(bool p_is_static);
	void parse_function_signature(FunctionNode *p_function, SuiteNode *p_body, const String &p_type);
	SuiteNode *parse_suite(const String &p_context, SuiteNode *p_suite = nullptr, bool p_for_lambda = false);
	
	AnnotationNode *parse_annotation(uint32_t p_valid_targets);
	bool register_annotation(const MethodInfo &p_info, uint32_t p_target_kinds, AnnotationAction p_apply, const Vector<Variant> &p_default_arguments = Vector<Variant>(), bool p_is_vararg = false);
	bool validate_annotation_arguments(AnnotationNode *p_annotation);
	void clear_unused_annotations();
	bool tool_annotation(const AnnotationNode *p_annotation, Node *p_target);
	bool icon_annotation(const AnnotationNode *p_annotation, Node *p_target);
	bool onready_annotation(const AnnotationNode *p_annotation, Node *p_target);
	template <PropertyHint t_hint, Variant::Type t_type>
	bool export_annotations(const AnnotationNode *p_annotation, Node *p_target);
	template <PropertyUsageFlags t_usage>
	bool export_group_annotations(const AnnotationNode *p_annotation, Node *p_target);
	bool warning_annotations(const AnnotationNode *p_annotation, Node *p_target);
	bool rpc_annotation(const AnnotationNode *p_annotation, Node *p_target);
	bool static_unload_annotation(const AnnotationNode *p_annotation, Node *p_target);
	
	Node *parse_statement();
	VariableNode *parse_variable(bool p_is_static);
	VariableNode *parse_variable(bool p_is_static, bool p_allow_property);
	VariableNode *parse_property(VariableNode *p_variable, bool p_need_indent);
	void parse_property_getter(VariableNode *p_variable);
	void parse_property_setter(VariableNode *p_variable);
	ConstantNode *parse_constant(bool p_is_static);
	AssertNode *parse_assert();
	BreakNode *parse_break();
	ContinueNode *parse_continue();