perf srcline: Do not return NULL for srcline

The code assumes non-NULL srcline value always, let's return the usual
SRCLINE_UNKNOWN ("??:0") string instead.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221215192817.2734573-2-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/srcline.c

@@ -716,7 +716,7 @@ char *__get_srcline(struct dso *dso, u64 addr, struct symbol *sym,
 
 	if (!show_addr)
 		return (show_sym && sym) ?
-			    strndup(sym->name, sym->namelen) : NULL;
+			    strndup(sym->name, sym->namelen) : SRCLINE_UNKNOWN;
 
 	if (sym) {
 		if (asprintf(&srcline, "%s+%" PRIu64, show_sym ? sym->name : "",