lack of result checking for hex.DecodeString in many places.

[Fyodor Ustinov]

If an empty string is passed to hex.DecodeString, it returns an empty string. Upon a cursory examination of the source code, it is evident that this is not checked anywhere. As a result, amusing messages like the following can occur:"

yggdrasilctl debug_remotegetself key=
Admin socket returned an error: timeout