Fail quickly in login tests if no username field

Change-Id: Ice02446e6cc07e3387073fc33d596a373dcc9fcd
diff --git a/lib/korap_rc.js b/lib/korap_rc.js
index 409e39e..ce6be0c 100644
--- a/lib/korap_rc.js
+++ b/lib/korap_rc.js
@@ -22,6 +22,8 @@
             await page.keyboard.press("Tab")
             await page.keyboard.type(password)
             await page.keyboard.press("Enter")
+        } else {
+            return false
         }
 
         await page.waitForNavigation();