implement et2_label_empty class for all set_label methods and remove no longer necessary label.et2_label > input[type="checkbox"], as it is covered by the standard case

api/js/etemplate/et2_extension_nextmatch.js

@@ -2873,8 +2873,10 @@ var et2_nextmatch_header = (function(){ "use strict"; return et2_baseWidget.exte
 		this.label = _value;
 
 		this.labelNode.text(_value);
+		
+		// add class if label is empty
+		this.labelNode.toggleClass('et2_label_empty', !_value);
 	}
-
 });}).call(this);
 et2_register_widget(et2_nextmatch_header, ['nextmatch-header']);