Restore the error handling logic so that when file measurement fails,
the respective iint entry is not left with the digest data being
populated with zeroes.

Fixes: 54f03916 ("ima: permit fsverity's file digests in the IMA measurement list")
Cc: stable@vger.kernel.org	# 5.19
Signed-off-by: Matt Bobrowski <mattbobrowski@google.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>