Logger fix.

Summary: This should be a temporary fix for logger. We won't emit anything. This is useful in case tests don't initialize logger.

Reviewers: mferencevic, buda, teon.banek

Reviewed By: teon.banek

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D209

src/logging/logger.hpp

@@ -36,7 +36,7 @@ class Logger {
 
   template <class Level, class... Args>
   void emit(Args &&... args) {
-    debug_assert(log != nullptr, "Log object has to be defined.");
+    if (log == nullptr) return;
 
     auto message = std::make_unique<Message<Level>>(
         Timestamp::now(), name, fmt::format(std::forward<Args>(args)...));