fix: weth unwrap swap review undefined

[DanielSinclair]

Fixes BX-1647 Figma link (if any):

What changed (plus any additional context for devs)

• sellAmountDisplay and buyAmountDisplay could be undefined for WETH unwrap quotes

Screen recordings / screenshots

What to test

• Tested both Optimism WETH -> ETH and Degen Chain WDEGEN to DEGEN

[linear[bot]]

BX-1647 Error swapping WETH from expanded state