These garbage references only show up when a DNS lookup rejects with an
Exception on legacy PHP <= 5.6. These issues have been fixed upstream in
the Promise component for current PHP versions with
https://github.com/reactphp/promise/releases/tag/v2.6.0 but this PR
explicitly unsets known garbage references to avoid unexpected memory
growth on legacy PHP versions.
The downstream Socket component implicitly depends on this because its
test suite currently fails. This changeset can be considered a new
feature in this component which fixes a bug in the test suite of a
downstream component.

jsor approved these changes Jul 10, 2019