Bug in Base58 implementation

[shargon]

Describe the bug
Base58 doesn't work as expected when dealing with empty arrays

To Reproduce
Steps to reproduce the behavior:

1. Create an empty array var data=new byte[32];
2. Try to encode and decode it
3. You won't obtain the same result

var buffer = new byte[32];
var str = Base58.Encode(buffer);
var deco = Base58.Decode(str);
if (!buffer.SequenceEqual(deco)) throw new Exception(); 

Expected behavior
Obtain the same encoded data

Screenshots

It was discovered during the red4sec fuzzing phase