updater: Skip empty lines in the transfer list file.

We have the last line being empty as a result of
android::base::Split("a\nb\n"), which leads to "missing command"
warnings in the update. Just skip all the empty lines.

Bug: 24373789
Change-Id: I5827e4600bd5cf0418d95477e4592fec47bbd3a9
1 file changed