ncd: modules: net_watch_interfaces: add missing error message

ncd/modules/net_watch_interfaces.c

@@ -360,6 +360,7 @@ static void func_new (NCDModuleInst *i)
     
     // compile regex
     if (regcomp(&o->preg, "/([^/]+)/net/", REG_EXTENDED)) {
+        ModuleLog(o->i, BLOG_ERROR, "regcomp failed");
         goto fail2;
     }