bug #867 Avoid displaying broken images in "show" view (javiereguiluz)

This PR was merged into the master branch.

Discussion
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Avoid displaying broken images in "show" view

| Before | After
| --- | ---
| ![before](https://cloud.githubusercontent.com/assets/73419/12867722/86d81532-ccf5-11e5-8446-6c6989da1b8c.png) | ![after](https://cloud.githubusercontent.com/assets/73419/12867724/8822001a-ccf5-11e5-8a8e-204ffd9241df.png)

Commits
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7970849 Avoid displaying broken images in "show" view

Twig/EasyAdminTwigExtension.php

@@ -140,6 +140,11 @@ public function renderEntityField(\Twig_Environment $twig, $view, $entityName, $
             }
 
             if ('image' === $fieldType) {
+                // avoid displaying broken images when the entity defines no image
+                if (empty($value)) {
+                    return $twig->render($entityConfiguration['templates']['label_empty'], $templateParameters);
+                }
+
                 // absolute URLs (http or https) and protocol-relative URLs (//) are rendered unmodified
                 if (1 === preg_match('/^(http[s]?|\/\/).*/i', $value)) {
                     $imageUrl = $value;