perf record: Fix a asan runtime error in util/maps.c

If I build perf with asan and run Zstd test:

$ make -C tools/perf O=/tmp/perf DEBUG=1 EXTRA_CFLAGS="-O0 -g -fno-omit-frame-pointer -fsanitize=undefined"
$ /tmp/perf/perf test "Zstd perf.data compression/decompression" -vv
83: Zstd perf.data compression/decompression:
...
util/maps.c:1046:5: runtime error: null pointer passed as argument 2, which is declared to never be null
...

The issue was caused by `bsearch`. The patch adds a check to ensure
argument 2 and 3 are not NULL and 0.

Testing with the commands above confirms that the runtime error is
resolved.

Reviewed-by: Ian Rogers <[e-mail]>
Signed-off-by: Chun-Tse Shao <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Ben Gainey <[e-mail]>
Cc: Christophe Leroy <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: James Clark <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Leo Yan <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Nick Terrell <[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/maps.c

···
 	while (!done) {
 		down_read(maps__lock(maps));
 		if (maps__maps_by_address_sorted(maps)) {
-			struct map **mapp =
-				bsearch(&ip, maps__maps_by_address(maps), maps__nr_maps(maps),
-					sizeof(*mapp), map__addr_cmp);
+			struct map **mapp = NULL;
+			struct map **maps_by_address = maps__maps_by_address(maps);
+			unsigned int nr_maps = maps__nr_maps(maps);
 
+			if (maps_by_address && nr_maps)
+				mapp = bsearch(&ip, maps_by_address, nr_maps, sizeof(*mapp),
+					       map__addr_cmp);
 			if (mapp)
 				result = map__get(*mapp);
 			done = true;