Fixed crash when continuing search after last result

git-svn-id: http://devserv/svn/fluxdvd/components/wxPDFView/trunk@8290 ee4118f4-65c3-8c42-83c6-dbb17464b6b1
Fixed search crash with backward search

git-svn-id: http://devserv/svn/fluxdvd/components/wxPDFView/trunk@8294 ee4118f4-65c3-8c42-83c6-dbb17464b6b1
Fixed crash while searching

git-svn-id: http://devserv/svn/fluxdvd/components/wxPDFView/trunk@8302 ee4118f4-65c3-8c42-83c6-dbb17464b6b1