BUG/MEDIUM: http-fetch: Don't fetch the method if there is no stream

The "method" sample fetch does not perform any check on the stream existence
before using it. However, for errors triggered at the mux level, there is no
stream. When the log message is formatted, this sample fetch must fail. It
must also fail when it is called from a health-check.

This patch must be backported as far as 2.4.
1 file changed