Merge pull request diasurgical#1849 from mewpull/pack-enum

pack: use IDI_GOLD enum instead of boolean operation for is->IDidx

Source/pack.cpp

@@ -25,7 +25,7 @@ static void PackItem(PkItemStruct *id, ItemStruct *is)
 			id->bMDur = is->_iMaxDur;
 			id->bCh = is->_iCharges;
 			id->bMCh = is->_iMaxCharges;
-			if (!is->IDidx)
+			if (is->IDidx == IDI_GOLD)
 				id->wValue = is->_ivalue;
 		}
 	}