Previously, `uv__udp_io` would proceed to call `uv__udp_recvmsg` for
the `POLLERR` event even if the handle was just closed by the `POLLIN`
callback.
This commit adds a guard to verify the handle is still active before
processing the error queue. It also adds a regression test that
mimics this recursive closure behavior.
Fixes: https://github.com/libuv/libuv/issues/5030
Signed-off-by: Juan José Arboleda <soyjuanarbol@gmail.com>
