Pass data through to ItemEffects.partyAction for Gen 2 pack items

Both call sites -- Game2:usePartyItem (the field pack) and
BattleState:useItem (the battle pack) -- asked ItemEffects.partyAction
for an item's family with no `data` argument, even though every other
call in the same functions (useOnMon, usePpItem, applyPartyItem) passed
it through correctly. partyAction resolves through recordFor, which
reads data.gen2ItemEffects when given a dataset and falls back to the
module's own built-in RECORDS table when not -- so with no data, a
mod's own item_effects record was invisible and every mod-defined Gen 2
field or battle item resolved to a nil action, falling straight through
to "isn't going to help here" / "isn't going to help here" without ever
opening the party picker.

Both now pass the live dataset (self.data on Game2, self.game.data on
the battle screen) the same way their sibling calls already did.

src/ui/gen2/BattleState.lua

@@ -3024,8 +3024,10 @@ function BattleState:useItem(itemId)
     -- Everything else the pack can spend on a party mon runs the same
     -- item_effects.asm routine the field pack runs: the potion line and the
     -- drinks, the status cures and their berries, REVIVE / MAX REVIVE, and
-    -- the ETHER / ELIXER family.
-    local action = ItemEffects.partyAction(itemId)
+    -- the ETHER / ELIXER family.  Without the merged dataset this can only
+    -- ever see RECORDS, the module's own built-ins, the same gap
+    -- Game2:usePartyItem had for the field pack.
+    local action = ItemEffects.partyAction(itemId, self.game and self.game.data)
     if action then
       return self:useOnPartyMon(itemId, action)
     end