DELETE YOUR CONFIG.YML BEFORE YOU UPDATE YOUR NICKAPI.

NickAPI v4.2 has been released!

Changelogs:
+ added a full support for cracked servers. This plugin can be used as a replacement for SkinRestorer
+ added a new method (see below)
* MojangAPI is now the default option on NickAPI. Of course you can change it within the API or in the config.yml
* fixed a bug that creates a infinite loop on onEnable method because of getting the skindata of the account "Steve"

Added method:
I heard that some of the people have problems because of the method refreshPlayer has a delay and people can't execute their codes because of appearance of race conditions. Because of it I added this method.
#isCurrentlyRefreshing will return true if refreshPlayer is still being executed.
To use this method, I recommend you to create an async task and execute a while loop to check whether this method returns false. Of course using an interface would be probably better, but I would've changed a huge amount of code stuff for that.
This method is experimental and could be removed in the next update!