Fixing a bug in HasDataPresenter where paging to a negative row index causes an IndexOutOfRange exception. We now properly trim the keyboard selected row to a non-negative value.

Issue: 6383

Review at http://gwt-code-reviews.appspot.com/1513804

Review by: rjrjr@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@10508 8db76d5a-ed1c-0410-87a9-c151d255dfc7