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
  --> 7b27a1b8214eb4f2bcd735707964c949ec41d9893ed2cbbde8b2f858178a7db2:31:15
   |
31 |     let nft <- parentRef!.withdraw(withdrawID: id)
   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `optional`, got `{NonFungibleToken.NFT}`