Bukkit

=== Brief error description ===
The follow book expressions either give internal errors or don't work properly: author of %itemstack%, pages of %itemstack%, book by author %author% with title %title% and pages %pages%)

Author and pages give internal errors, and giving a player a book via "book by %author% with title %title%..." gives an unauthored untitled book with *Invalid book tag* inside.

=== What causes this error? Please paste the exact line you used ===
I'm using the examples from skUnity, e.g.:

set {_Author} to author of player's tool
send "%{_Author}%" to player

=== Please use Pastebin.com and paste the error you get, then paste the URL here ===
Stacktrace for author expression: http://pastebin.com/3dp4eFi8
Stacktrace for pages expression: http://pastebin.com/JgYewBJv

Also if I execute them in game with | it says it's executing and then I just say it in chat. Presumably because the expressions aren't working at all.

=== What server version are you using? Latest is not an answer! Use /ver and tell me ===
https://gyazo.com/9a7a52b09b95bccac439547011a41772

=== What Umbaska version are you using? If you're using a BETA version please paste the ID ===
1.5.2_JAVA7