An oversight in an earlier commit led to a memory leak
in the untypical situation that zlib instances are created
but never used, because zlib handles no longer started
out their life as weak handles.
The bug was introduced in bd201102862a194f3f5ce669e0a3c8143eafc900.
Refs: https://github.com/nodejs/node/pull/20455
PR-URL: https://github.com/nodejs/node/pull/21607
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
