Avoid missing reference types.

themes/root/templates/RecordDriver/AbstractBase/export-refworks.phtml

 <?
 // A driver-specific template may pass in format overrides; check for these before going to the driver itself:
 $formats = isset($this->overrideFormats) ? $this->overrideFormats : $this->driver->tryMethod('getFormats');
-if (is_array($formats)) {
+if (is_array($formats) && !empty($formats)) {
     foreach ($formats as $format) {
         echo "RT $format\n";
     }
+} else {
+    echo "RT Generic\n";
 }
 
 $title = rtrim($this->driver->getTitle(), " /");