I downloaded the product code from the github page.Compile on the eclipse.
I tried to login according to my registration information from the login page opened on
localhost but after giving the error message I mentioned earlier and a blank page is displayed.

 Error
com.vaadin.server.ServerRpcManager$RpcInvocationException: Unable to invoke method click in com.vaadin.shared.ui.button.ButtonServerRpc-----

Error
com.vaadin.server.ServerRpcManager$RpcInvocationException: Unable to invoke method call in com.vaadin.ui.JavaScript$JavaScriptCallbackRpc

And 

blank page appears