Fixed the last session extra scripts still printed on __SessionList__

[liming01]

This PR fixed session with extra scripts, the last file can not be filtered. Below is the sample:

The files:

➜ [/Users/gpadmin/.vim/sessions] ls
hawq2 hawq2x.vim postgres postgres-xl postgres-xlx.vim postgresx.vim

The session list window shows as below:

 1 "-----------------------------------------------------
2 " q - close session list
3 " o, <CR>, <2-LeftMouse> - open session
4 " d - delete session
5 " e - edit session
6 " x - edit extra session script
7 "-----------------------------------------------------
8
9 hawq2
10 postgres
11 postgres-xl
12 postgresx.vim

We need to filter the last item which is a session extra script.