code: function blockFilter( isOutput, fillEmptyBlock ) {
  
  			return function( block ) {
  				// DO NOT apply the filler if it's a fragment node.
  				if ( block.type == CKEDITOR.NODE_DOCUMENT_FRAGMENT )
  					return;
  
  				cleanBogus( block );
  
  				var shouldFillBlock = typeof fillEmptyBlock == 'function' ? fillEmptyBlock( block ) : fillEmptyBlock;
  
  				if ( shouldFillBlock !== false && isEmptyBlockNeedFiller( block ) ) {
  					block.add( createFiller( isOutput ) );
  				}
  			};
  		}
docs: This text block filter, remove any bogus and create the filler on demand.