Devel::Events::Filter::HandlerOptional - A role for filters that are useful even without a handler.

	package MyFilter;
	use Moose;

	with qw/Devel::Events::Filter::HandlerOptional/;

	sub filter_event {
		# do something
	}

This is just like Devel::Events::Filter except it won't complain if handler is unset, but instead just drop events.

Deve::Events::Filter::Warn