2 May 29, 2016 19:23
I don't think this qualifies as an error but rather as a matter of taste.
Anyways, we hear you and we'll include a search field by default on the 404 in an upcoming release.
Furthermore, to make it easy to configure, we'll include a container so you can set you own widgets, including search field; quickly and easily.
In the meantime, you can always customize the 404 page of you skins to make it display exactly what you want, but I guess you know that as you already looked into the code.