### 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
int len = length();
	if (len == 0) {
		return false;
	}
	int from = 0;
	if (len != 1 && (operator[](0) == '+' || operator[](0) == '-')) {
		from++;
	}
	if (p_with_prefix) {
		if (len < 3) {
			return false;
		}
		if (operator[](from) != '0' || operator[](from + 1) != 'x') {
			return false;
		}
		from += 2;
	}
	for (int i = from; i < len; i++) {
		char32_t c = operator[](i);
		if (is_hex_digit(c)) {
			continue;
		}
		return false;
	}
	return true;
}
bool ::is_valid_float() const {