Delete portmap failed (i.e.,) delete portmap alone which is configured in vbridge interfaces

When i delete portmap which is created under vbridge interface, it throws Internal ServerError. Used lateest Stable/Be branch

Steps which i followed to delete portmap.

1) Create VTN, VBR
2) Create Vbridge Interface
3) Create vbr interface Portmap
$) Failed - Delete portmap --> Throws Internal Server Error.