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.