Fix lstopo text in case of null cpusets
Fix lstopo text in case of null cpusets

This commit was SVN r1649.

ggouaillardet/hwloc,shekkbuilder/hwloc,ggouaillardet/hwloc,shekkbuilder/hwloc,shekkbuilder/hwloc,ggouaillardet/hwloc,ggouaillardet/hwloc,shekkbuilder/hwloc