perf sort: Fix segfault with basic block 'cycles' sort dimension

Skip the sample which doesn't have branch_info to avoid segmentation
fault:

The fault can be reproduced by:

  perf record -a
  perf report -F cycles

Signed-off-by: Changbin Du <changbin.du@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: 0e332f0 ("perf tools: Add support for cycles, weight branch_info field")
Link: http://lkml.kernel.org/r/20170313083148.23568-1-changbin.du@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/sort.c

@@ -846,13 +846,18 @@ static int hist_entry__mispredict_snprintf(struct hist_entry *he, char *bf,
 static int64_t
 sort__cycles_cmp(struct hist_entry *left, struct hist_entry *right)
 {
+	if (!left->branch_info || !right->branch_info)
+		return cmp_null(left->branch_info, right->branch_info);
+
 	return left->branch_info->flags.cycles -
 		right->branch_info->flags.cycles;
 }
 
 static int hist_entry__cycles_snprintf(struct hist_entry *he, char *bf,
 				    size_t size, unsigned int width)
 {
+	if (!he->branch_info)
+		return scnprintf(bf, size, "%-.*s", width, "N/A");
 	if (he->branch_info->flags.cycles == 0)
 		return repsep_snprintf(bf, size, "%-*s", width, "-");
 	return repsep_snprintf(bf, size, "%-*hd", width,