perf dlfilter: Be defensive against potential NULL dereference

In the unlikely case of having a symbol without a mapping, avoid a
NULL dereference that clang-tidy warns about.
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Yang Jihong <yangjihong1@huawei.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: llvm@lists.linux.dev
Cc: Ming Wang <wangming01@loongson.cn>
Cc: Tom Rix <trix@redhat.com>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20231009183920.200859-11-irogers@google.comSigned-off-by: Namhyung Kim <namhyung@kernel.org>

tools/perf/util/dlfilter.c

@@ -52,8 +52,10 @@ static void al_to_d_al(struct addr_location *al, struct perf_dlfilter_al *d_al)
 		d_al->sym_end = sym->end;
 		if (al->addr < sym->end)
 			d_al->symoff = al->addr - sym->start;
-		else
+		else if (al->map)
 			d_al->symoff = al->addr - map__start(al->map) - sym->start;
+		else
+			d_al->symoff = 0;
 		d_al->sym_binding = sym->binding;
 	} else {
 		d_al->sym = NULL;