Merge pull request #1013 from LamarLugli/bugfix-1012

#1012 Fixed exception when consumer tag cannot be found in the consumers dictionary

(cherry picked from commit d39bb71)

Author: michaelklishin

projects/RabbitMQ.Client/client/impl/ModelBase.cs

@@ -459,7 +459,7 @@ public void OnSessionShutdown(object sender, ShutdownEventArgs reason)
             SetCloseReason(reason);
             OnModelShutdown(reason);
             BroadcastShutdownToConsumers(_consumers, reason);
-            ConsumerDispatcher.Shutdown(this).GetAwaiter().GetResult();;
+            ConsumerDispatcher.Shutdown(this).GetAwaiter().GetResult(); ;
         }
 
         protected void BroadcastShutdownToConsumers(Dictionary<string, IBasicConsumer> cs, ShutdownEventArgs reason)
@@ -625,8 +625,10 @@ public void HandleBasicCancel(string consumerTag, bool nowait)
             IBasicConsumer consumer;
             lock (_consumers)
             {
-                consumer = _consumers[consumerTag];
-                _consumers.Remove(consumerTag);
+                if (_consumers.TryGetValue(consumerTag, out consumer))
+                {
+                    _consumers.Remove(consumerTag);
+                }
             }
             if (consumer == null)
             {
@@ -646,12 +648,24 @@ public void HandleBasicCancelOk(string consumerTag)
                             consumerTag
                             ));
             */
+            IBasicConsumer consumer;
+
             lock (_consumers)
             {
-                k.m_consumer = _consumers[consumerTag];
-                _consumers.Remove(consumerTag);
+                if (_consumers.TryGetValue(consumerTag, out consumer))
+                {
+                    k.m_consumer = consumer;
+                    _consumers.Remove(consumerTag);
+                }
             }
+
+            if (consumer == null)
+            {
+                k.m_consumer = DefaultConsumer;
+            }
+
             ConsumerDispatcher.HandleBasicCancelOk(k.m_consumer, consumerTag);
+
             k.HandleCommand(IncomingCommand.Empty); // release the continuation.
         }
 
@@ -679,7 +693,7 @@ public virtual void HandleBasicDeliver(string consumerTag,
             IBasicConsumer consumer;
             lock (_consumers)
             {
-                consumer = _consumers[consumerTag];
+                _consumers.TryGetValue(consumerTag, out consumer);
             }
             if (consumer == null)
             {