Replace this:

;; Probhat Input Method
(quail-define-package
"probhat" "Bengali-probhat" "probhat" t
"Porbhat for Bangla" nil t nil nil nil nil nil nil nil nil t)

with this please:

;; Probhat Input Method
(quail-define-package "Probhat" "Bengali" "bengali-probhat" t "Probhat for Bangla" nil t nil nil nil nil nil nil nil nil t)

in the file "lisp/leim/quail/indian.el"

On Mon, Jun 27, 2016 at 8:42 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> Date: Mon, 27 Jun 2016 01:55:38 +0600
> From: উৎসব রায় <uroybd@gmail.com>
> Cc: emacs-devel@gnu.org
>
> Yes yes, in the last mail i mentioned about that typo and fixed layout name also. :)

Please send a patch against what's in the repository.

Thanks.