Fixes #6884 - simply fail when Piwik is already installed to prevent other issues

plugins/Installation/Controller.php

@@ -78,26 +78,20 @@ class Controller extends \Piwik\Plugin\ControllerAdmin
      * Installation Step 1: Welcome
      *
      * Can also display an error message when there is a failure early (eg. DB connection failed)
-     *
-     * @param string Optional error message
      */
-    function welcome($message = false)
+    function welcome()
     {
         // Delete merged js/css files to force regenerations based on updated activated plugin list
         Filesystem::deleteAllCacheOnUpdate();
 
-        if (empty($message)) {
-            $this->checkPiwikIsNotInstalled();
-        }
+        $this->checkPiwikIsNotInstalled();
         $view = new View(
             '@Installation/welcome',
             $this->getInstallationSteps(),
             __FUNCTION__
         );
 
-        $view->newInstall = !SettingsPiwik::isPiwikInstalled();
-        $view->errorMessage = $message;
-        $view->showNextStep = $view->newInstall;
+        $view->showNextStep = true;
         return $view->render();
     }
 

plugins/Installation/templates/welcome.twig

@@ -3,15 +3,7 @@
 {% block content %}
 <h2>{{ 'Installation_Welcome'|translate }}</h2>
 
-{% if newInstall %}
-    {{ 'Installation_WelcomeHelp'|translate(totalNumberOfSteps)|raw }}
-{% else %}
-    <p>{{ 'Installation_ConfigurationHelp'|translate }}</p>
-    <br/>
-    <div class="error">
-        {{ errorMessage }}
-    </div>
-{% endif %}
+{{ 'Installation_WelcomeHelp'|translate(totalNumberOfSteps)|raw }}
 
 <script type="text/javascript">
     <!--