Test flake: Create series by filling all fields

[php-coder]

Create series by filling all fields :: Verify creation of series b... | FAIL |
The element seems to be disconnected from the DOM.  This means that a user cannot interact with it.
For documentation on this error, please visit: http://seleniumhq.org/exceptions/stale_element_reference.html
Build info: version: '2.53.1', revision: 'a36b8b1cd5757287168e54b817830adce9b0158d', time: '2016-06-30 19:26:09'
System info: host: 'testing-gce-21bd936a-fc4e-42e7-8786-c0f35c6451a9', ip: '127.0.1.1', os.name: 'Linux', os.arch: 'amd64', os.version: '3.13.0-103-generic', java.version: '1.8.0_111'
Driver info: driver.version: HtmlUnitDriver

See here: https://travis-ci.org/php-coder/mystamps/jobs/215324328

[php-coder]

Yet another one: https://travis-ci.org/php-coder/mystamps/jobs/215324328