Added support for optional columns in db

src/admin/common/abstract/model.php

@@ -117,6 +117,9 @@ abstract class AbstractCommonClubsModel
             if($v['type'] !== 'ref')
                 continue;
             
+            if(is_null($vals[$k]))
+                continue;
+            
             $vals[$k] = $vals[$k]->getId();
         }
         
@@ -133,6 +136,9 @@ abstract class AbstractCommonClubsModel
             if(empty($v['ref']))
                 throw new Exception('External reference of unknown class found.');
             
+            if(empty($vals[$k]))
+                continue;
+            
             $vals[$k] = $this->loadExternalReferenceAsObject($v['ref'], $vals[$k]);
         }
         
@@ -304,6 +310,7 @@ abstract class AbstractCommonClubsModel
         $q->where("id = {$this->id}");
     }
     
+    // FIXME Add additional filter to remove associations of the object
     public function delete()
     {
         $db = Factory::getDbo();