### Godot version

4.1.1

### System information

linux

### Issue description

The `"%+f"` format adds a `+` sign in front of positive numbers. If you try to format `-0.0`, it breaks and displays both a `+` and a `-`.

### Steps to reproduce

```gdscript
@tool
extends EditorScript

func _run() -> void:
    print("%+f" % -0.0)
```

### Minimal reproduction project

see above
formatted;
	char32_t *self = (char32_t *)get_data();
	bool in_format = false;
	int value_index = 0;
	int min_chars = 0;
	int min_decimals = 0;
	bool in_decimals = false;
	bool pad_with_zeros = false;
	bool left_justified = false;
	bool show_sign = false;
	if (error) {
		*error = true;
	}
	for (; *self; self++) {
		const char32_t c = *self;
		if (in_format) { // 
			switch (c) {
				case '%': { // 
					formatted += chr(c);
					in_format = false;
					break;