perf hists browser: Refuse 'a' hotkey on non symbolic views

We don't allocate the histogram data structures for --sort lists without
"sym", so, just like was done for the menu, don't try to annotate when
'a' is pressed, just warn the user about it.
Reported-by: David Ahern <dsahern@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-27mjg02s2mbw8lfxqv7jpzec@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/ui/browsers/hists.c

@@ -882,6 +882,13 @@ static int perf_evsel__hists_browse(struct perf_evsel *evsel, int nr_events,
 			 */
 			goto out_free_stack;
 		case 'a':
+			if (!browser->has_symbols) {
+				ui__warning(
+			"Annotation is only available for symbolic views, "
+			"include \"sym\" in --sort to use it.");
+				continue;
+			}
+
 			if (browser->selection == NULL ||
 			    browser->selection->sym == NULL ||
 			    browser->selection->map->dso->annotate_warned)