diff --git a/controller/Database.py b/controller/Database.py
index c6ea4b7..141ac79 100644
--- a/controller/Database.py
+++ b/controller/Database.py
@@ -259,7 +259,7 @@ class Valid_id( object ):
     self.__none_okay = none_okay
 
   def __call__( self, value ):
-    if self.__none_okay and value is None: return None
+    if self.__none_okay and value in ( None, "" ): return None
     if self.ID_PATTERN.search( value ): return str( value )
 
     raise ValueError()