Core/AH: Fix memory leak

Fix memory leak in Auction House when creating an auction with stackable items and a stack of the same amount in the inventory. Leak added in 15a2acfb528728b824291cb49cdd9196e6f0d57d .
Core/Misc: Fix warning

Partially revert f0a742a8c471ba948d5d86c1ab5e3a74329a9a92 to fix a warning about unhandled switch case (the same case that Coverity reported as dead code) .