Fix mingw32 compilation

include/spdlog/details/mpmc_blocking_q.h

@@ -85,6 +85,7 @@ public:
         std::unique_lock<std::mutex> lock(queue_mutex_);
         q_.push_back(std::move(item));
         push_cv_.notify_one();
+
     }
 
     // try to dequeue item. if no item found. wait upto timeout and try again
@@ -96,7 +97,8 @@ public:
         {
             return false;
         }
-        q_.pop_front(popped_item);
+        popped_item = std::move(q_.front());
+        q_.pop_front();
         pop_cv_.notify_one();
         return true;
     }