fix: Use return value of _renderVarDisplay_image horde/turba#16 horde/turba#16

Also requires a change in horde/form

Author: Horde Release

lib/Horde/Core/Ui/VarRenderer/Html.php

@@ -1278,7 +1278,7 @@ protected function _renderVarDisplay_image($form, &$var, &$vars)
         $image = $var->getValue($vars);
 
         /* Check if existing image data is being loaded. */
-        $var->type->loadImageData($image);
+        $image = $var->type->loadImageData($image);
 
         if (empty($image['img'])) {
             return '';