Can't bump Jetty to 9.4.45

[tresf]

When attempting to bump Jetty to 9.4.45, I receive the following NullPointerException:

java.lang.NullPointerException: Cannot invoke "org.eclipse.jetty.websocket.server.NativeWebSocketConfiguration.addMapping(org.eclipse.jetty.http.pathmap.PathSpec, org.eclipse.jetty.websocket.servlet.WebSocketCreator)" because "this.configuration" is null
	at org.eclipse.jetty.websocket.server.WebSocketUpgradeFilter.addMapping(WebSocketUpgradeFilter.java:157)
	at qz.ws.PrintSocketServer.runServer(PrintSocketServer.java:167)
	at qz.ws.PrintSocketServer.main(PrintSocketServer.java:113)

Upon further investigation, it appears there was a change to how WebsocketUpgradeFilter.configure(...) initializes its internal configuration object. I'm not sure if this change was intentional.

A temporary workaround is to fallback to the @Deprecated configureContext(...) API call, however this is just a stop-gap as the permanent solution is to ensure the filter's internal configuration isn't null.

[tresf]

Closed via #943, #936