net/http: nil pointer dereference panic for httputil.ReverseProxy users [1.21 backport]

[gopherbot]

@neild requested issue #53808 to be considered for backport to the next 1.21 minor release.

@gopherbot please open backport issues. This causes panics for ReverseProxy users, with no workaround.

[dmitshur]

See #67375 (comment).

[mdempsky]

Rejected as won't fix. @dmitshur mentions this caused a test to become flaky.