Treasure Caskets - Fix data type passed to messageSpecial, remove unused local variable

[ghost]

I affirm:

• [x] that I agree to Topaz Next's Limited Contributor License Agreement, as written on this date
• [x] that I have read the Contributing Guide and the Code of Conduct
• [x] that I've tested my code since the last commit in the PR, and will test after any later commits

Temporary:

• [x] that I understand there are large refactoring efforts going on right now, that these efforts touch every single Lua script and binding, and that my pull request might get put on hold to ensure there are not any conflicts with the refactoring work

messageSpecial was receiving string type, and defaulting to 0 for some values. Fix involved casting values placed into splitNumbers table, and removing additional casts sprinkled around the lua afterwards. Also, removed one reference to splitNumbers that was not used.

Fixes #2534