return null;
playerStack = inventoryPlayer.getStackInSlot( buttonPressed );
if( playerStack == null ) {
inventoryPlayer.setInventorySlotContents( buttonPressed, stackInSlot );
slot.onPickupFromSlot( player, stackInSlot );
} else {
int indx = inventoryPlayer.getFirstEmptyStack();
if( indx > -1 ) {
inventoryPlayer.setInventorySlotContents( buttonPressed, stackInSlot );
inventoryPlayer.addItemStackToInventory( playerStack );