use appropriate default for channel owner username

app/views/admin/venue/channel/editor.pug

@@ -61,7 +61,7 @@ block content
           div(class="uk-width-1-1 uk-width-1-2@s")
             label(for="owner").uk-form-label Owner
             .uk-form-controls
-              input(type="text", name="owner", placeholder=`Enter channel owner's local username (here on ${site.name})`, value= channel ? channel.owner.username : 'rob').uk-input
+              input(type="text", name="owner", placeholder=`Enter channel owner's local username (here on ${site.name})`, value= channel ? channel.owner.username : user.username).uk-input
 
           div(class="uk-width-1-1 uk-width-1-2@s")
             label(for="sort-order").uk-form-label Sort order