Fix problem with isset

classes/Formo/ORM.php

@@ -108,7 +108,7 @@ public function get_form( array $fields, Formo $form = NULL)
 				}
 			}
 
-			if ( ! isset($this->$field_name))
+			if ($this->_field_exists($field_name) !== TRUE)
 			{
 				// Custom method looks like _formo_$field_name()
 				$method = '_formo_'.$field_name;
@@ -234,6 +234,15 @@ protected static function _get_field_name( ORM $model)
 		return $field_name;
 	}
 
+	protected function _field_exists($column)
+	{
+		return (array_key_exists($column, $this->_object) OR
+			array_key_exists($column, $this->_related) OR
+			array_key_exists($column, $this->_has_one) OR
+			array_key_exists($column, $this->_belongs_to) OR
+			array_key_exists($column, $this->_has_many));
+	}
+
 	/**
 	 * Fills $this->_foreign_keys in order to easier
 	 * find foreign keys in all the process_type methods