Can we get an error, if the script is running without Solr is running?

Steps to reproduce

• Start updatesearchindexsolr.php when Solr isn't running
• The only indication that something is wrong is this PHP warning, which is shown once for each object indexed:
  PHP Warning: DOMDocument::loadXML(): Empty string supplied as input in /home/gl/svn/ezfind/ezp4/trunk/extension/ezfind/classes/ezsolrbase.php on line 271
  PHP Stack trace:
  PHP 1. {main}

  () /home/gl/svn/ezfind/ezp4/trunk/extension/ezfind/bin/php/updatesearchindexsolr.php:0
  PHP 2. ezfUpdateSearchIndexSolr->run() /home/gl/svn/ezfind/ezp4/trunk/extension/ezfind/bin/php/updatesearchindexsolr.php:60
  PHP 3. ezfUpdateSearchIndexSolr->runSubProcess() /home/gl/svn/ezfind/ezp4/trunk/extension/ezfind/bin/php/updatesearchindexsolr.php:156
  PHP 4. eZSolr->addObject() /home/gl/svn/ezfind/ezp4/trunk/extension/ezfind/bin/php/updatesearchindexsolr.php:199
  PHP 5. eZSolrBase->addDocs() /home/gl/svn/ezfind/ezp4/trunk/extension/ezfind/search/plugins/ezsolr/ezsolr.php:579
  PHP 6. eZSolrBase::validateUpdateResult() /home/gl/svn/ezfind/ezp4/trunk/extension/ezfind/classes/ezsolrbase.php:345
  PHP 7. DOMDocument->loadXML() /home/gl/svn/ezfind/ezp4/trunk/extension/ezfind/classes/ezsolrbase.php:271