It looks like this should have been caught by CI but there might have been a conflict with a recently merged PR like #19101. Failure was reported by fanquake #22219 (comment)
Fix avoids null WalletClient pointer dereference in address book test by adding MakeWalletClient call and making address book test initialization more consistent with wallet test initialization:
https://github.com/bitcoin/bitcoin/blob/865ee1af201238f48671e3b79b8215f896db7a05/src/qt/test/addressbooktests.cpp#L63-L66 https://github.com/bitcoin/bitcoin/blob/865ee1af201238f48671e3b79b8215f896db7a05/src/qt/test/wallettests.cpp#L141-L144