### 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
CHECK(String::chr(0x20d812)[0] == 0xfffd); 
	ERR_PRINT_ON
}
TEST_CASE("[String] Operator []") {
	String a = "Kugar Sane";
	a[0] = 'S';
	a[6] = 'C';
	CHECK(a == "Sugar Cane");
	CHECK(a[1] == 'u');
	CHECK(a.unicode_at(1) == 'u');
}
TEST_CASE("[String] Case function test") {
	String a = "MoMoNgA";
	CHECK(a.to_upper() == "MOMONGA");
	CHECK(a.to_lower() == "momonga");
}
TEST_CASE("[String] Case compare function test") {
	String a = "MoMoNgA";
	CHECK(a.casecmp_to("momonga") != 0);
	CHECK(a.nocasecmp_to("momonga") == 0);
}
TEST_CASE("[String] Natural compare function test") {
	String a = "img2.png";
	CHECK(a.nocasecmp_to("img10.png") > 0);
	CHECK(a.naturalnocasecmp_to("img10.png") < 0);
}
TEST_CASE("[String] hex_encode_buffer") {
	static const uint8_t u8str[] = { 0x45, 0xE3, 0x81, 0x8A, 0x8F, 0xE3 };
	String s = String::hex_encode_buffer(u8str, 6);
	CHECK(s == U"45e3818a8fe3");