fix a few leaks by throwing objects, not newed pointers to objects

src/cryptonote_core/blockchain.cpp

@@ -471,7 +471,7 @@ bool Blockchain::deinit()
   // memory operation), otherwise we may cause a loop.
   if (m_db == NULL)
   {
-    throw new DB_ERROR("The db pointer is null in Blockchain, the blockchain may be corrupt!");
+    throw DB_ERROR("The db pointer is null in Blockchain, the blockchain may be corrupt!");
   }
 
   try