Resolve "Error caused by display format"

Closes #5 (closed)

src/Plugin/views/style/HorizontalBoxes.php

@@ -33,14 +33,34 @@ class HorizontalBoxes extends DefaultStyle
 
     protected $usesoptions = true;
 
-
     protected $renderFields = true;
 
+	/**
+	 * Defines the initial options of the Horizontal Boxes.
+	 *
+	 * @return mixed
+	 */
     protected function defineOptions(){
       $options = parent::defineOptions();
-      $options['row_class'] = 'horizontal-boxes-row';
-      $options['default_row_class'] = 'horizontal-boxes-row';
+      $options['row_class'] = array('default'=> 'horizontal-boxes-row') ;
       return $options;
     }
 
-}
+	/**
\ No newline at end of file
+	 * Overrides the options form of HB
+	 *
+	 * @param $form
+	 * @param FormStateInterface $form_state
+	 */
+	public function buildOptionsForm(&$form, FormStateInterface $form_state) {
+		parent::buildOptionsForm($form, $form_state);
+
+		$form['row_class'] = array(
+				'#type' => 'textfield',
+				'#title' => t('Row Class'),
+				'#default_value' => (isset($this->options['row_class'])) ? $this->options['row_class'] : 'horizontal-boxes-row',
+		);
+    }
+
+
+	}
\ No newline at end of file