I am trying to connect to a server, but after I click to get on, the screen shows "java.lang.NullPointerException: group"

In the launcher log, it looks like this:
15:26:50.527
Couldn't connect to server java.lang.NullPointerException: group at io.netty.bootstrap.AbstractBootstrap.group(AbstractBootstrap.java:80) at ek.a(SourceFile:275) at bei$1.run(SourceFile:59)
 

This is in 1.9 but it won't let me enter that.