Imported entries which fail to fetch get standard error body

src/Wallabag/ImportBundle/Import/ChromeImport.php

@@ -37,7 +37,7 @@ class ChromeImport extends BrowserImport
     {
         $data = [
             'title' => $entry['name'],
-            'html' => '',
+            'html' => false,
             'url' => $entry['url'],
             'is_archived' => $this->markAsRead,
             'tags' => '',

src/Wallabag/ImportBundle/Import/FirefoxImport.php

@@ -37,7 +37,7 @@ class FirefoxImport extends BrowserImport
     {
         $data = [
             'title' => $entry['title'],
-            'html' => '',
+            'html' => false,
             'url' => $entry['uri'],
             'is_archived' => $this->markAsRead,
             'tags' => '',

src/Wallabag/ImportBundle/Import/InstapaperImport.php

@@ -76,6 +76,7 @@ class InstapaperImport extends AbstractImport
                 'is_starred' => $data[3] === 'Starred',
                 'content_type' => '',
                 'language' => '',
+                'html' => false,
             ];
         }
         fclose($handle);

src/Wallabag/ImportBundle/Import/ReadabilityImport.php

@@ -103,6 +103,7 @@ class ReadabilityImport extends AbstractImport
             'is_archived' => $importedEntry['archive'] || $this->markAsRead,
             'is_starred' => $importedEntry['favorite'],
             'created_at' => $importedEntry['date_added'],
+            'html' => false,
         ];
 
         $entry = new Entry($this->user);