Transaction

[Error Code: 1101] error caused by: 1 error occurred:
	* transaction preprocess failed: [Error Code: 1101] cadence runtime error: Execution failed:
error: cannot apply binary operation ?? to left-hand type
  --> a5f8b33c281af817199afdea1f4dfbeb9c2d72d58c5d3e4129ee67ba1035a9ec:31:15
   |
31 |     let nft <- parentRef!.withdraw(withdrawID: id)
   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `optional`, got `{NonFungibleToken.NFT}`