Logo doesn't appear

Hi Tom

A couple days ago everything was ok, but today I discovered that logo doesn't appear, on it's place I see an alt text. it appears under the customize->Site Identity->logo but not in the header. The site is on localhost and that's why I can't provide the link on it. so here is the HTML which I see while inspecting.

<a href="http://localhost/" title="unistyle" rel="home">
<img src="" alt="unistyle" title="unistyle"/>
</a>

do you have any considerations what can it be, why src doesn't get an image link?

Best regards MK