The previous patch loading utilities omitted empty patches, as they
were thought to be of no significance, and when no patches were used,
the import and therefore dependency should not be used. If a user has
added an empty patch file, and made an entry in the order file, the QA
would treat this as an error as it had no means of differentiating
between a patch not present and an empty patch.

This patch fixes the solution by better handling empty patches, and
logging warnings when they are encountered.

Signed-off-by: Hrvoje Ribicic <riba@google.com>
Reviewed-by: Michele Tartara <mtartara@google.com>