Fixed a critical issue for all melee attacks, where the damage was reduced twice if a player attacked another player.

Might be related to: bugreport:6991

Thanks to playtester for helping me to test my fix.

git-svn-id: https://rathena.svn.sourceforge.net/svnroot/rathena/trunk@17216 54d463be-8e91-2dee-dedb-b68131a5f0ec