perf tools: Fix segfault when using srcline sort key

The srcline sort key is for grouping samples based on their source file
and line number.  It use addr2line tool to get the information but it
requires dso name.  It caused a segfault when a sample does not have the
name by dereferencing a NULL pointer.  Fix it by using raw ip addresses
for those samples.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1350272383-7016-1-git-send-email-namhyung@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>