Keys of just 1 char gives error

[emandtf]

I have a very big JSON and some key:value pairs are similar to this:
['p' => '1234']

but this library gives an error because the Key is just 1 char:
return Compressor::create()->compress(['p' => '1234'])->toJson();

If the Key becomes "pp" it works fine.

The error is located here:

php-compress-json / src / DataTypes / JsonString.php : 10

in this method:

public static function encodeString(string $str): string {
$prefix = $str[0] . $str[1]; <-- HERE BECAUSE IF THE KEY IS JUST "p" THE INDEX [1] DOESN'T EXISTS