Update js/grid.celledit.js

Correct the scroll page bug when clicking on a non-editable cell when celledit mode is active. This bug can be seen only in Chrome.
It can be reproduced with this test case :
http://jsfiddle.net/lgoncalves/zcm2C/
I apply the suggestion of sergey68 in 
http://www.trirand.com/blog/?page_id=393/bugs/grid-scrolls-to-top-after-selecting-a-cell/page-2/
and with this correction the bug is corrected.
Merge pull request #428 from laurentgoncalves/patch-3

Update js/grid.celledit.js