Increment loop index whether or not command succeeded. Fixes BUKKIT-5455

When VanillaCommandWrapper dispatches a command containing a
PlayerSelector wtih c>-1 (implicitly true for @a), it loops over the
selected players and exectures the command with each player. However, the
loop index is only incremented if the command fails. As a result, a
successful command is repeated on the same player indefinitely, locking up
the server. This commit fixes the issue by incrementing the loop index
regardless of whether the command succeeds, ensuring the command is only
executed once per player identified by the PlayerSelector.