Release lock before notify

src/zm_db.cpp

@@ -237,8 +237,12 @@ zmDbQueue::~zmDbQueue() {
 }
 
 void zmDbQueue::stop() {
+  {
+    std::unique_lock<std::mutex> lock(mMutex);
     mTerminate = true;
+  }
   mCondition.notify_all();
+
   if (mThread.joinable()) mThread.join();
 }