Ensure proxyauth has a fallback icon for apps without icons

src/proxyauth.js

@@ -152,7 +152,7 @@ async function login(req, res, next) {
 
     const data = {
         loginUrl: `https://${dashboardFqdn}/openid/auth?client_id=${proxyAuthClientId}&scope=openid profile email&response_type=code&redirect_uri=https://${app.fqdn}/callback`,
-        iconUrl: `https://${dashboardFqdn}${app.iconUrl}`,
+        iconUrl: app.iconUrl ? `https://${dashboardFqdn}${app.iconUrl}` : `https://${dashboardFqdn}/img/appicon_fallback.png`,
         name: app.label || app.subdomain || app.fqdn,
         language: await settings.get(settings.LANGUAGE_KEY),
         apiOrigin: `https://${dashboardFqdn}`,