Omeka has encountered an error

Exception

"400" Status: Bad Request

Backtrace

exception 'Exception' with message '"400" Status: Bad Request' in /var/www/html/plugins/SolrSearch/models/lib/Service.php:334
Stack trace:
#0 /var/www/html/plugins/SolrSearch/models/lib/Service.php(964): Apache_Solr_Service->_sendRawGet('http://localhos...')
#1 /var/www/html/plugins/SolrSearch/controllers/ResultsController.php(62): Apache_Solr_Service->search('(    OR tt:   ^...', 0, '30', Array)
#2 /var/www/html/application/libraries/Zend/Controller/Action.php(513): SolrSearch_ResultsController->indexAction()
#3 /var/www/html/application/libraries/Zend/Controller/Dispatcher/Standard.php(289): Zend_Controller_Action->dispatch('indexAction')
#4 /var/www/html/application/libraries/Zend/Controller/Front.php(946): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#5 /var/www/html/application/libraries/Zend/Application/Bootstrap/Bootstrap.php(77): Zend_Controller_Front->dispatch()
#6 /var/www/html/application/libraries/Zend/Application.php(358): Zend_Application_Bootstrap_Bootstrap->run()
#7 /var/www/html/application/libraries/Omeka/Core.php(157): Zend_Application->run()
#8 /var/www/html/index.php(30): Omeka_Core->run()
#9 {main}