Some of the things are missing. Please update or confirm your files as shown below:
webapp.gwt.xml: (add rename-to and change source path)
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE module SYSTEM "gwt-module.dtd">
<module rename-to='myapp'>
<inherits name='com.google.gwt.user.User'/>
<!-- Specify the app entry point class. -->
<entry-point class='myapp.admin.webapp.client.AdminEntryPoint'/>
<source path='client'/>
</module>
myapp-admin.html: (conform below line)
<script type="text/javascript" src="myapp/myapp.nocache.js"></script>
Delete all GWT cache files and start a fresh GWT compile before running your application.