libganglia: avoid NULL pointer dereference if passed a NULL hash
libganglia: avoid NULL pointer dereference if passed a NULL hash

reported by Bernard to segfault a 3.1.0 gmetad aggregator of 3.1.0 leafs.


git-svn-id: 27e0aca8c7a52a9ae65dfba2e16879604119af8c@1631 93a4e39c-3214-0410-bb16-828d8e3bcd0f

fastly/ganglia,fastly/ganglia,fastly/ganglia,fastly/ganglia,fastly/ganglia