Warning: array_flip(): Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->load()

If we have no bids but auction is expired we try to load user with uid = NULL. I got these errors:

Warning: array_flip(): Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->load() (line 178 of includes/entity.inc).
Notice: Trying to get property of non-object in uc_auction_cron() (line 720 of sites/all/modules/indev/uc_auction/uc_auction.module).

Patch attached. Thanks!

Hunks may exist because of my previous patches #1367198: SQL exception editing product if not auction, #1556830: Notice: Undefined property: stdClass::$is_auc em uc_auction_form_alter() .