make sure that the async handler is properly stopped when the database is closed or destructed

src/database.cc

@@ -214,6 +214,11 @@ int Database::EIO_Close(eio_req *req) {
     Baton* baton = static_cast<Baton*>(req->data);
     Database* db = baton->db;
 
+    if (db->debug_trace) {
+        delete db->debug_trace;
+        db->debug_trace = NULL;
+    }
+
     baton->status = sqlite3_close(db->handle);
 
     if (baton->status != SQLITE_OK) {
@@ -472,6 +477,11 @@ void Database::Destruct(Persistent<Value> value, void *data) {
 int Database::EIO_Destruct(eio_req *req) {
     Database* db = static_cast<Database*>(req->data);
 
+    if (db->debug_trace) {
+        delete db->debug_trace;
+        db->debug_trace = NULL;
+    }
+
     sqlite3_close(db->handle);
     db->handle = NULL;