Combine.mac to destroy

[JDEKnox]

#event OutOfStuff "Sorry, but you don't have everything you need for this recipe in your general inventory." 
  
Sub Main 
:Loop 
 
:dest
/if (${Me.Skill[Pottery]}<=301) /nomodkey /ctrl /itemnotify ${FindItem[=Unfired Star Ruby Encrusted Stein].InvSlot} leftmouseup
/if (${Cursor.ID}) {
/destroy
/goto :ClearCursor
}
:ClearCursor
/if (${Cursor.ID}) {
/autoinventory 
/goto :dest 
} 
 
/notify TradeskillWnd CombineButton leftmouseup 
/doevents 
/delay 2
/notify TradeskillWnd AutoInvButton leftmouseup
/goto :Loop 
/return 
 
Sub Event_OutOfStuff 
/endmacro 
/return

so my problem is i keep getting spammed with Invalid Item slot 'null'
What can i do to change this around and get rid of it?