perf tools: Fix report -F symbol_to for data without branch info

The branch field sorting code assumes hist_entry::branch_info is
allocated, which is wrong and following perf session ends up with report
segfault.

  $ perf record ls
  $ perf report -F symbol_to
  perf: Segmentation fault

Checking that hist_entry::branch_info is valid and display "N/A" string
in snprint callback if it's not.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1413468427-31049-5-git-send-email-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/sort.c

@@ -413,8 +413,13 @@ sort__sym_from_cmp(struct hist_entry *left, struct hist_entry *right)
 static int64_t
 sort__sym_to_cmp(struct hist_entry *left, struct hist_entry *right)
 {
-	struct addr_map_symbol *to_l = &left->branch_info->to;
-	struct addr_map_symbol *to_r = &right->branch_info->to;
+	struct addr_map_symbol *to_l, *to_r;
+
+	if (!left->branch_info || !right->branch_info)
+		return cmp_null(left->branch_info, right->branch_info);
+
+	to_l = &left->branch_info->to;
+	to_r = &right->branch_info->to;
 
 	if (!to_l->sym && !to_r->sym)
 		return _sort__addr_cmp(to_l->addr, to_r->addr);
@@ -434,10 +439,14 @@ static int hist_entry__sym_from_snprintf(struct hist_entry *he, char *bf,
 static int hist_entry__sym_to_snprintf(struct hist_entry *he, char *bf,
 				       size_t size, unsigned int width)
 {
-	struct addr_map_symbol *to = &he->branch_info->to;
-	return _hist_entry__sym_snprintf(to->map, to->sym, to->addr,
-					 he->level, bf, size, width);
+	if (he->branch_info) {
+		struct addr_map_symbol *to = &he->branch_info->to;
+
+		return _hist_entry__sym_snprintf(to->map, to->sym, to->addr,
+						 he->level, bf, size, width);
+	}
 
+	return repsep_snprintf(bf, size, "%-*.*s", width, width, "N/A");
 }
 
 struct sort_entry sort_dso_from = {