Fix HttpCallListener when Mink driver is not started yet

.travis.yml

@@ -1,6 +1,6 @@
 language: php
 
-dist: trusty
+dist: xenial
 
 addons:
   chrome: stable

src/Context/BrowserContext.php

@@ -25,7 +25,9 @@ public function __construct($timeout = 1)
      */
     public function closeBrowser()
     {
-        $this->getSession()->stop();
+        if ($this->getMink()->isSessionStarted()) {
+            $this->getSession()->stop();
+        }
     }
 
     /**

src/HttpCall/HttpCallListener.php

@@ -51,9 +51,11 @@ public function afterStep(AfterStepTested $event)
         // For now to avoid modification on MinkContext
         // We add fallback on Mink
         try {
-            $this->httpCallResultPool->store(
-                new HttpCallResult($this->mink->getSession()->getPage()->getContent())
-            );
+            if ($this->mink->getSession()->isStarted()) {
+                $this->httpCallResultPool->store(
+                    new HttpCallResult($this->mink->getSession()->getPage()->getContent())
+                );
+            }
         } catch (\LogicException $e) {
             // Mink has no response
         } catch (\Behat\Mink\Exception\DriverException $e) {

tests/features/browser.feature

@@ -1,8 +1,12 @@
 Feature: Browser Feature
 
+    @javascript
+    Scenario: Testing when scenario has no HTTP call
+        Given I wait 0.1 seconds
+
     # If this scenario fails
     # It's probably because your web environment is not properly setup
-    # You will find the necessery help in README.md
+    # You will find the necessary help in README.md
     @javascript
     Scenario: Testing simple web access
         Given I am on "/index.html"