title: Error "Call to a member function get() on null" on Running acceptance with Codeception 2.2.10 on Windows
body: <p>I'm using Codeception for acceptance testing. Selenium driver version <strong>3.3.1</strong> (selenium-server-standalone-3.3.1.jar) along with latest version of firefox <strong>52</strong> to test. I've already added geckodriver version 0.15 to the environment variable Path of Windows. But when running an acceptance test, I get the following error :</p>
  
  <p><strong>"[Error] Call to a member function get() on null "</strong></p>
  
  <p>In addition, I get the following warning in the selenium running terminal :</p>
  
  <p><strong>"The path to the driver executable must be set by the webdriver.gecko.driver system property"</strong></p>
  
  <p>The following is my acceptance.suite.yml file: </p>
  
  <pre><code>class_name: AcceptanceTester
      modules:
          enabled:
              - WebDriver:
              url: 'http://www.test.com/'
              browser: 'firefox'
              - Asserts
              - \Helper\Acceptance
  </code></pre>
  
  <p>To run the selenium driver, I run the following command: </p>
  
  <pre><code>java -jar tests\selenium-server-standalone-3.3.1.jar
  </code></pre>
  
  <p>And to run the test, I run the following command:</p>
  
  <pre><code>vendor\bin\codecept run tests\acceptance\TestCest.php
  </code></pre>
  
  <p>Does selenium can not read the path from environment variable Path of Windows? </p>