Wait for stale indicator to disappear before clicking bake.

As the new inputWorker is slower, nightwatch was clicking cancel and thus showing the stale indicator.

tests/browser/nightwatch.js

@@ -82,6 +82,7 @@ module.exports = {
         browser
             .useCss()
             .setValue("#input-text", "Don't Panic.")
+            .waitForElementNotVisible("#stale-indicator", 1000)
             .click("#bake");
 
         // Check output