syslogd: do not segfault on parse error when using default config. Closes 5762

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/sysklogd/syslogd.c b/sysklogd/syslogd.c
index f349f47..3fe3f53 100644
--- a/sysklogd/syslogd.c
+++ b/sysklogd/syslogd.c
@@ -429,7 +429,9 @@
 	return;
 
  cfgerr:
-	bb_error_msg_and_die("error in '%s' at line %d", file, parser->lineno);
+	bb_error_msg_and_die("error in '%s' at line %d",
+			file ? file : "/etc/syslog.conf",
+			parser->lineno);
 }
 #endif