title: The activator for bundle is invalid
body: <p>I'm trying to create a simple plugin in eclipse. When I run the application, I see this error in log file:</p>
  
  <blockquote>
    <p>org.osgi.framework.BundleException : The activator for bundle
    org.x.y.Activator for bundle org.x.y is invalid.</p>
  </blockquote>
  
  <p>Do you have any idea about this error?</p>