Crash when clicking on the button 'Back to server list' in some cases

java.lang.NullPointerException: Ticking screen
	at io.netty.bootstrap.Bootstrap.checkAddress(Bootstrap.java:358)
	at io.netty.bootstrap.Bootstrap.doResolveAndConnect(Bootstrap.java:180)
	at io.netty.bootstrap.Bootstrap.connect(Bootstrap.java:162)
	at io.netty.bootstrap.Bootstrap.connect(Bootstrap.java:143)
	at brk.b(SourceFile:241)
	at brk.a(SourceFile:45)
	at brk$1.a(SourceFile:144)
	at gg.l(SourceFile:379)
	at brk.a(SourceFile:254)
	at bmh.e(SourceFile:115)
	at bhc.t(SourceFile:1596)
	at bhc.ax(SourceFile:964)
	at bhc.a(SourceFile:404)
	at net.minecraft.client.main.Main.main(SourceFile:123)