Can attempt message send without subscribers

- Change state assert not to throw if we're in state
  where message would never get consumed. Now
  just returning false.
- Fixes #1002

spring-shell-core/src/main/java/org/springframework/shell/component/view/event/DefaultEventLoop.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023 the original author or authors.
+ * Copyright 2023-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -45,7 +45,6 @@
 import org.springframework.shell.component.view.control.ViewEvent;
 import org.springframework.shell.component.view.event.processor.AnimationEventLoopProcessor;
 import org.springframework.shell.component.view.event.processor.TaskEventLoopProcessor;
-import org.springframework.util.Assert;
 
 /**
  * Default implementation of an {@link EventLoop}.
@@ -202,8 +201,11 @@ public void onDestroy(Disposable disposable) {
 	// }
 
 	private boolean doSend(Message<?> message, long timeout) {
-		Assert.state(this.active && this.many.currentSubscriberCount() > 0,
-				() -> "The [" + this + "] doesn't have subscribers to accept messages");
+		if (!this.active || this.many.currentSubscriberCount() == 0) {
+			return false;
+		}
+		// Assert.state(this.active && this.many.currentSubscriberCount() > 0,
+		// 		() -> "The [" + this + "] doesn't have subscribers to accept messages");
 		long remainingTime = 0;
 		if (timeout > 0) {
 			remainingTime = timeout;

spring-shell-core/src/test/java/org/springframework/shell/component/view/event/DefaultEventLoopTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023 the original author or authors.
+ * Copyright 2023-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -120,6 +120,15 @@ void canDispatchMono() {
 		verifier1.verify(Duration.ofSeconds(1));
 	}
 
+
+	@Test
+	void dispatchNoSubscribersDoesNotError() {
+		initDefault();
+		Message<String> message = MessageBuilder.withPayload("TEST").build();
+
+		loop.dispatch(message);
+	}
+
 	@Test
 	void subsribtionCompletesWhenLoopDestroyed() {
 		initDefault();