Fixing method call bug in canBeReviewedBy() (#1)

If getOptions returns false, then canBeReviewedBy() throws "Call to a member function OwnerGroups() on boolean".
This will return false, in the the case that options are false.

code/extensions/SiteTreeContentReview.php

@@ -453,6 +453,10 @@ class SiteTreeContentReview extends DataExtension implements PermissionProvider
         }
 
         $options = $this->getOptions();
+        
+        if (!$options) {
+            return false;
+        }
 
         if ($options->OwnerGroups()->count() == 0 && $options->OwnerUsers()->count() == 0) {
             return false;