Infinite loop in modInverse on negative number #27

When invoking modInverse on BigInteger object representing negative number, library seems to fall into an infinite loop.

Example code:

    new BigInteger('-3').modInverse(new BigInteger('2'));

Expected behaviour:
Return a value

Actual behaviour:
Infinite loop

Known workaround:
Invoking mod before modInverse:

    const p = new BigInteger('2');
    new BigInteger('-3').mod(p).modInverse(p);