Ignore empty loads files -- it seems scp in OpenSSH sometimes leaves

files empty even if the original target and the new source are both
non-empty.  (Old ssh1 never did that, but whether this is a bug is not
obvious.)

Tools/portbuild/scripts/checkmachines

@@ -16,7 +16,11 @@ while true; do
     l=$2
     if [ -f ${buildroot}/loads/$m -a \
       ! -z "$(find ${buildroot}/loads/$m -newer ${stamp})" ]; then
-      num=$(cat ${buildroot}/loads/$m)
+      num=$(awk '{print $1}' ${buildroot}/loads/$m)
+      if [ "x$num" = "x" ]; then
+	logger "checkmachines: file ${buildroot}/loads/$m is empty"
+	num=99
+      fi
     else
       num=99
     fi