Fix http listener

[adrienbrault]

[thmsbernard]

I have an error:

[2020-04-01 12:26:53] php.CRITICAL: Uncaught Error: Call to a member function waitForLoad() on null {"exception":"[object] (Error(code: 0): Call to a member function waitForLoad() on null at /Project//vendor/dmore/chrome-mink-driver/src/ChromeDriver.php:1279)"}

Your fix fix this issue as it is caused by the line:

new HttpCallResult($this->mink->getSession()->getPage()->getContent())

When I execute a step before the Mink sessions seems to have started