Backport of Core PR14728: fix uninitialized read when stringifying an addrLocal

Summary:
This is a backport of Core PR14728

As above. https://github.com/bitcoin/bitcoin/pull/14728

Test Plan:

ninja check

Reviewers: jasonbcox, O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D4570