List index too large, showing data in colin tree from firebase

Help Me!!!

Please give some hint to get rid of this error.

The runtime error tells that list you are getting has two elements but you are trying to get third item.

wait. keep online. I have understood but i will be back soon

The error message says it all.
       Attempted to get item number 3 of a list which's length is 2.

The problem is here:

See, you added an item to a list, and the item is a 3rd item of an unknown list. There’s probably less items then 3 in that list.

ONT Studios