fix crash searching newsgroup which you've never opened r=alecf 45028

mailnews/base/search/src/nsMsgSearchNews.cpp

@@ -408,6 +408,8 @@ void nsMsgSearchNews::ReportHits ()
     err = scopeFolder->GetDBFolderInfoAndDB(getter_AddRefs(folderInfo), getter_AddRefs(db));
   }
 
+  if (db)
+  {
 	  for (PRUint32 i = 0; i < m_hits.GetSize(); i++)
 	  {
       nsCOMPtr <nsIMsgDBHdr> header;
@@ -416,6 +418,7 @@ void nsMsgSearchNews::ReportHits ()
 		  if (header)
 			  ReportHit(header, scopeFolder);
 	  }
+  }
 }
 
 // ### this should take an nsIMsgFolder instead of a string location.