fix(instances): an address search after the session ends goes to the login form

The search's request was sent on to the login page, and the dialog said
"The search did not go through. Try again." The page now reloads, which
goes to the login form and back to the Instances page after signing in.

static/js/find_address.js

@@ -100,6 +100,11 @@
         button.disabled = true;
         var url = text.url + "?" + new URLSearchParams({q: form.elements.q.value});
         fetch(url, {headers: {"X-Requested-With": "XMLHttpRequest"}}).then(function (response) {
+            if (response.redirected) {
+                // signed out meanwhile: reloading goes to the login form, then back here
+                location.reload();
+                return new Promise(function () {});
+            }
             return response.json();
         }).catch(function () {
             return {error: text.failed};