setHeader("Cookie", "=foo")

Exception level 0: java.lang.StringIndexOutOfBoundsException: String index out of range: 0
	at java.lang.String.charAt(String.java:646)
	at io.undertow.util.Cookies.createCookie(Cookies.java:277)
	at io.undertow.util.Cookies.parseCookie(Cookies.java:254)
	at io.undertow.util.Cookies.parseRequestCookies(Cookies.java:181)
	at io.undertow.server.HttpServerExchange.getRequestCookies(HttpServerExchange.java:1003)
	at io.undertow.server.session.SessionCookieConfig.findSessionId(SessionCookieConfig.java:83)
	at io.undertow.servlet.spec.SessionCookieConfigImpl.findSessionId(SessionCookieConfigImpl.java:58)
	at org.wildfly.extension.undertow.session.CodecSessionConfig.findSessionId(CodecSessionConfig.java:56)
	at io.undertow.server.session.InMemorySessionManager.getSession(InMemorySessionManager.java:142)
	at io.undertow.servlet.spec.ServletContextImpl.getSession(ServletContextImpl.java:677)
	at io.undertow.servlet.spec.ServletContextImpl.getSession(ServletContextImpl.java:707)
	at io.undertow.servlet.spec.ServletContextImpl.updateSessionAccessTime(ServletContextImpl.java:711)
	at io.undertow.servlet.spec.HttpServletResponseImpl.responseDone(HttpServletResponseImpl.java:522)
	at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:287)
	at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:227)
	at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:73)
	at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:146)
	at io.undertow.server.Connectors.executeRootHandler(Connectors.java:177)
	at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:727)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)