htmlParser not recognizing empty comments

[Piotrek Koszuliński]

var counter = 0,
	parser = new CKEDITOR.htmlParser();

parser.onComment = function( comment )
	{
		counter += 1;
	};

parser.parse( '<!---->' );
assert.areSame( 1, counter ); // error (actual: 0)

[Piotrek Koszuliński]

Basic dt test available on t/8640: ​http://ckeditor4.t/dt/core/htmlparser/htmlparser.html

[Jakub Ś]

Other related to problems with HTML comments: #8732, #8569, #8216, #8129, #6709

[Jakub Ś]

Still reproducible in latest CKEditor 4.5.3