### Godot version

4.0 beta17

### System information

Windows10

### Issue description

call `"".split()`
Is there an infinite loop inside? Function does not return.

### Steps to reproduce

"".split()

### Minimal reproduction project

N/A
if (!p_str || p_str[0] == 0) {
		return *this;
	}
	const int lhs_len = length();
	const size_t rhs_len = strlen(p_str);
	resize(lhs_len + rhs_len + 1);
	char32_t *dst = ptrw() + lhs_len;
	for (size_t i = 0; i <= rhs_len; i++) {
		uint8_t c = p_str[i] >= 0 ? p_str[i] : uint8_t(256 + p_str[i]);
		if (c == 0 && i < rhs_len) {
			print_unicode_error("NUL character", true);
			dst[i] = 0x20;
		} else {
			dst[i] = c;
		}
	}
	return *this;
}
String &String::operator+=(const wchar_t *p_str) {
#ifdef WINDOWS_ENABLED
	
	*this += String::utf16((const char16_t *)p_str);
#else
	
	*this += String((const char32_t *)p_str);
#endif
	return *this;
}
String &String::operator+=(const char32_t *p_str) {