title: Why streams in Dart isolates doesn't work without receive port
body: <p>I have a strange problem when i try to use a stream inside an isolate,
  if i try something like this </p>
  
  <pre><code>main() async {
    await Isolate.spawn(entryPoint, null);
  }
  
  entryPoint(SendPort sendPort) {
    getStreamOfNumbers().listen((data) =&gt; print('data : $data'));
  }
  
  Stream&lt;int&gt; getStreamOfNumbers() async* {
    for (int x = 0; x &lt; 10; x++) yield x;
  }
  </code></pre>
  
  <p>nothing is printed into the console , but if i add a receive port inside the main method it works fine
  ,even if i don't use the receive port</p>
  
  <pre><code> main() async {
    ReceivePort receivePort = ReceivePort();
    await Isolate.spawn(entryPoint, null);
  }
  
  //the output is : 
  //data : 0
  //data : 1
  //data : 2
  //data : 3
  //data : 4
  //data : 5
  //data : 6
  //data : 7
  //data : 8
  //data : 9
  </code></pre>
  
  <p>is this a bug or i have something wrong ?</p>