items: add BUGFIX for RndItem, invalid logic for Scroll of Resurrect

[mewmew]

Scroll of Resurrect occurs twice in the item data list, firstly at IDI_RESURRECT with IDROP_NEVER, and secondly a regular item with IDROP_REGULAR.

Since the ri-- logic only checks for spell ID, ri will be decremented also for IDROP_NEVER; thus unintentionally removing the previously added valid item ID in Single Player (which is this case is always gold).

Therefore, the chance for gold drop is higher in Multi Player than Single Player.