perf evlist: Destructors should accept NULL

And do nothing, just like free(), to avoid having to test it in callers,
usually in error paths.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-mexbavy0ft387j5w89t365eu@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-kvm.c

@@ -1429,7 +1429,6 @@ static int kvm_events_live(struct perf_kvm_stat *kvm,
 	if (kvm->session)
 		perf_session__delete(kvm->session);
 	kvm->session = NULL;
-	if (kvm->evlist)
 	perf_evlist__delete(kvm->evlist);
 
 	return err;

tools/perf/tests/event-times.c

@@ -200,7 +200,6 @@ static int test_times(int (attach)(struct perf_evlist *),
 		 count.ena, count.run);
 
 out_err:
-	if (evlist)
 	perf_evlist__delete(evlist);
 	return !err ? TEST_OK : TEST_FAIL;
 }

tools/perf/tests/parse-no-sample-id-all.c

@@ -44,7 +44,6 @@ static int process_events(union perf_event **events, size_t count)
 	for (i = 0; i < count && !err; i++)
 		err = process_event(&evlist, events[i]);
 
-	if (evlist)
 	perf_evlist__delete(evlist);
 
 	return err;

tools/perf/util/evlist.c

@@ -127,6 +127,9 @@ void perf_evlist__exit(struct perf_evlist *evlist)
 
 void perf_evlist__delete(struct perf_evlist *evlist)
 {
+	if (evlist == NULL)
+		return;
+
 	perf_evlist__munmap(evlist);
 	perf_evlist__close(evlist);
 	cpu_map__put(evlist->cpus);