Correctly adjust mirror url (#6593)

templates/repo/settings/options.tmpl

@@ -62,7 +62,7 @@
 						<label for="interval">{{.i18n.Tr "repo.mirror_interval"}}</label>
 						<input id="interval" name="interval" value="{{.MirrorInterval}}">
 					</div>
-					<div class="field">
+					<div class="field {{if .Err_MirrorAddress}}error{{end}}">
 						<label for="mirror_address">{{.i18n.Tr "repo.mirror_address"}}</label>
 						<input id="mirror_address" name="mirror_address" value="{{.Mirror.FullAddress}}" required>
 						<p class="help">{{.i18n.Tr "repo.mirror_address_desc"}}</p>