Fix pager bug in search page

`PagerModule::Write` without any custom arguments has been erroneously used. Replaced it with `$this->Pager` (which gets initialized in the SearchController) and its method `ToString`. A hint have been that the wrong pager expressed "Next" while the controller sets `$this->Pager->MoreCode = 'More Results';`     
    
Tested successfully with search words that yield       
0 result,   
1 result,   
2 results and    
more than C('Garden.Search.PerPage') results