Fix to skill_blockpc_end

Duplicate indexes would not be cleared, causing array to gradually increase in size.
Thanks to ToiletMaster for providing extra information.

Signed-off-by: shennetsind <ind@henn.et>
Merge branch 'master' of https://github.com/HerculesWS/Hercules
Merge branch 'master' of https://github.com/HerculesWS/Hercules into ghbb