### 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
}
		space_prefix = String(" ").repeat(i - 2);
	}
	while (comments.has(line)) {
		if (!comments[line].new_line || !comments[line].comment.begins_with("##")) {
			break;
		}
		String doc_line = comments[line++].comment.trim_prefix("##");
		String title, link; 
		if (state == DOC_LINE_NORMAL) {
			
			String stripped_line = doc_line.strip_edges();
			if (stripped_line.is_empty()) {
				if (mode == BRIEF && !p_brief.is_empty()) {
					mode = DESC;
				}
				continue;
			} else if (stripped_line.begins_with("@tutorial")) {
				int begin_scan = String("@tutorial").length();
				if (begin_scan >= stripped_line.length()) {
					continue; 
				}
				if (stripped_line[begin_scan] == ':') { 
					
					title = "";
					link = stripped_line.trim_prefix("@tutorial:").strip_edges();
				} else {
					/* Syntax:
					 *   @tutorial ( The Title Here )         :         https://the.url/
					 *             ^ open           ^ close   ^ colon   ^ url