Throw QueueStateIsEmptyException when entering next state from empty queue

RedCatEngineUnityProject/Packages/StateMachine/Exceptions/QueueStateIsEmptyException.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace RedCatEngine.StateMachine.Exceptions
+{
+	public class QueueStateIsEmptyException : Exception
+	{
+		public string StateMachineName;
+
+		public QueueStateIsEmptyException(string stateMachineName)
+			: base(string.Format("Queue is empty in state machine {0}", stateMachineName))
+		{
+			StateMachineName = stateMachineName;
+		}
+	}
+}

RedCatEngineUnityProject/Packages/StateMachine/StateMachines/BaseTypedStateMachine.cs

@@ -78,6 +78,9 @@ public ITypedQueueStateMachine Enter<TState, TPayload>(TPayload payload)
 
 		public ITypedQueueStateMachine EnterNextFromQueue()
 		{
+			if (_queue.Count == 0)
+				throw new QueueStateIsEmptyException(_name);
+
 			var data = _queue.Dequeue();
 			AddToHistory(data);
 			var nextState = SelectStateAsActive(data.StateType);
@@ -152,4 +155,4 @@ protected virtual TBaseState GetState(Type type)
 			return targetState;
 		}
 	}
-}
+}

RedCatEngineUnityProject/Packages/StateMachine/Tests/ExceptionStateMachineTests.cs

@@ -48,5 +48,26 @@ public void GivenStateMachine_WhenEnterUnknownState_ThenCatchNotFoundStateExcept
 
 			Assert.IsTrue(false, "Not catch exception");
 		}
+
+		[Test]
+		public void GivenStateMachine_WhenEnterNextFromEmptyQueue_ThenCatchQueueStateIsEmptyException()
+		{
+			try
+			{
+				_stateMachine.EnterNextFromQueue();
+			}
+			catch (Exception exception)
+			{
+				Assert.IsTrue(
+					exception is QueueStateIsEmptyException,
+					"Catch incorrect error");
+				Assert.IsTrue(
+					exception.Message.Contains("TestedTypedStateMachine"),
+					"State machine name is not specified in exception message");
+				return;
+			}
+
+			Assert.IsTrue(false, "Not catch exception");
+		}
 	}
-}
+}