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
  --> 57fac73b3d679f388db022c378c2d00dd3e0d481174f39854a34680b0e8a3fda:31:15
   |
31 |     let nft <- parentRef!.withdraw(withdrawID: id)!
   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `optional`, got `{NonFungibleToken.NFT}`