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 <[e-mail]>
Acked-by: Ian Rogers <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Leo Yan <[e-mail]>
Cc: Milian Wolff <[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/srcline.c

···
 
 	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 : "",