Response on HEAD request

[mstup]

Passed an exception in console in response on HEAD request.

WARNING: sendResponseHeaders: being invoked with a content length for a HEAD request
java.io.IOException: response headers not sent yet
	at jdk.httpserver/sun.net.httpserver.PlaceholderOutputStream.checkWrap(Unknown Source)
	at jdk.httpserver/sun.net.httpserver.PlaceholderOutputStream.write(Unknown Source)
	at com.github.arteam.embedhttp.EmbeddedHttpServer.lambda$start$0(EmbeddedHttpServer.java:80)
	at jdk.httpserver/com.sun.net.httpserver.Filter$Chain.doFilter(Unknown Source)
	at jdk.httpserver/sun.net.httpserver.AuthFilter.doFilter(Unknown Source)
	at jdk.httpserver/com.sun.net.httpserver.Filter$Chain.doFilter(Unknown Source)
	at jdk.httpserver/sun.net.httpserver.ServerImpl$Exchange$LinkHandler.handle(Unknown Source)
	at jdk.httpserver/com.sun.net.httpserver.Filter$Chain.doFilter(Unknown Source)
	at jdk.httpserver/sun.net.httpserver.ServerImpl$Exchange.run(Unknown Source)
	at jdk.httpserver/sun.net.httpserver.ServerImpl$DefaultExecutor.execute(Unknown Source)
	at jdk.httpserver/sun.net.httpserver.ServerImpl$Dispatcher.handle(Unknown Source)
	at jdk.httpserver/sun.net.httpserver.ServerImpl$Dispatcher.run(Unknown Source)
	at java.base/java.lang.Thread.run(Unknown Source)

For the HEAD request method, there should be no body in response (not empty string).
The "Content-Length" header should be able to specify by exact number and later should be not overwritten.