Better handle empty package lists.

The fix in a294a46fb9 was not enough.
This should finally resolve the problem when a package list ends
up empty (most notably due to #if evaluating to false).

Sponsored-By: Offensive Security

debian/changelog

@@ -1,3 +1,9 @@
+live-build (1:20160105) UNRELEASED; urgency=medium
+
+  * Better handle empty package lists.
+
+ -- Raphaël Hertzog <hertzog@debian.org>  Tue, 05 Jan 2016 18:03:44 +0100
+
 live-build (1:20151215) unstable; urgency=medium
 
   * QA Upload.

scripts/build/binary_package-lists

@@ -145,6 +145,10 @@ then
 
 	for SECTION in ${POOL}/*
 	do
+		if [ ! -d "${SECTION}" ]; then
+			break # Do nothing if the package lists were empty...
+		fi
+
 		SECTION="$(basename ${SECTION})"
 
 		mkdir -p ${DISTS}/${LB_PARENT_DISTRIBUTION}/${SECTION}/binary-${LB_ARCHITECTURES}