directory listing with static server fails with exception

[ashertarno]

an attempt to use directory listing through StaticServer.staticServer().setDirectoryListing( true )
throws

ContextImpl Unhandled exception java.lang.NullPointerException
at java.lang.String.replace(String.java:2227)
at io.vertx.ext.apex.addons.impl.StaticServerImpl.lambda$sendDirectory$20(StaticServerImpl.java:433)...

the reason for such behavior is a lack of "title" value in routing context's data map:

directoryTemplate.replace("{title}", context.get("title")).replace("{directory}", normalizedDir)

it's not clear either how to set the title or why is it mandatory at all.