perf annotate-data: Ensure the number of type histograms

Arnaldo reported that there is a case where nr_histograms and histograms
don't agree each other.

It ended up in a segfault trying to access a NULL histograms array.

Let's make sure to update the nr_histograms when the histograms array is
changed.

Reported-by: Arnaldo Carvalho de Melo <[e-mail]>
Reviewed-by: Ian Rogers <[e-mail]>
Signed-off-by: Namhyung Kim <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/annotate-data.c

···
 	sz += sizeof(struct type_hist_entry) * adt->self.size;
 
 	/* Allocate a table of pointers for each event */
-	adt->nr_histograms = nr_entries;
 	adt->histograms = calloc(nr_entries, sizeof(*adt->histograms));
 	if (adt->histograms == NULL)
 		return -ENOMEM;
···
 		if (adt->histograms[i] == NULL)
 			goto err;
 	}
+
+	adt->nr_histograms = nr_entries;
 	return 0;
 
 err:
···
 {
 	for (int i = 0; i < adt->nr_histograms; i++)
 		zfree(&(adt->histograms[i]));
+
 	zfree(&adt->histograms);
+	adt->nr_histograms = 0;
 }
 
 void annotated_data_type__tree_delete(struct rb_root *root)