Check for errors when reading the headers following the pax headers.
Fixes#11169.
Change-Id: Ifec4a949ec8df8b49fa7cb7a67eb826fe2282ad8
Reviewed-on: https://go-review.googlesource.com/11031
Reviewed-by: Russ Cox <rsc@golang.org>
Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>