Remove redundant NULL checks after new
Remove redundant NULL checks after new

Summary:
Partial backport of Core PR10898 (commit 55224af)
https://github.com/bitcoin/bitcoin/pull/10898/commits/55224af6bdecf79bb0d2c95b16f1ff60b16c45f8

Test Plan: ninja check

Reviewers: deadalnix, Fabien, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2622

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