Looking at data/talkactions/scripts/create_item.lua, it looks like Player:addItem() returns nil if it didn't add the item and the added item's userdata or a table of userdata values on success, so you could do like so:
local c = {
itemId = 2148,
amount = 1,
newPos = {x = 677, y = 639, z = 7},
}...