fixing the bug in local searching in case of non-empty group and rules and OR operation

Hello Tony,

it seems to me that I found simple and safe way to fix the bug described in [the bug report](http://www.trirand.com/blog/?page_id=393/bugs/bug-in-local-searching/#p28113). The solution is very easy. It seems that sorting works fine with non-empty group and **empty rule**. So I suggest to move the `rules` part in one more additional group. An example of such transformation you can find in [the answer](http://stackoverflow.com/a/14521000/315935).

[The demo](http://www.ok-soft-gmbh.com/jqGrid/SearchingDialogAboveGrid1.htm) demonstrate the fix.

Best regards
Oleg