fix two nitpicks from clang-scan

- utils.c: overflowing size_t is basically impossible, but well...
- stats.c: NULL would probably not cause a problem with zero length passed

lib/utils.c

@@ -143,7 +143,10 @@ char* kr_strcatdup(unsigned n, ...)
 	for (unsigned i = 0; i < n; ++i) {
 		char *item = va_arg(vl, char *);
 		const size_t new_len = total_len + strlen_safe(item);
-		if (unlikely(new_len < total_len)) return NULL;
+		if (unlikely(new_len < total_len)) {
+			va_end(vl);
+			return NULL;
+		}
 		total_len = new_len;
 	}
 	va_end(vl);

modules/stats/stats.c

@@ -313,7 +313,7 @@ static char* stats_list(void *env, struct kr_module *module, const char *args)
 	size_t args_len = args ? strlen(args) : 0;
 	for (unsigned i = 0; i < metric_const_end; ++i) {
 		struct const_metric_elm *elm = &const_metrics[i];
-		if (strncmp(elm->key, args, args_len) == 0) {
+		if (args && strncmp(elm->key, args, args_len) == 0) {
 			json_append_member(root, elm->key, json_mknumber(elm->val));
 		}
 	}