function emptyLines( lines ) {
	var count;
	var i;

	count = 0;
	for ( i = 0; i < lines.length; i++ ) {
		if ( trim( lines[ i ] ) === '' ) {
			count += 1;
		}
	}
	return count;
}
Counts the number of empty lines.

@private
@param {StringArray} lines - source code lines
@returns {NonNegativeInteger} number of empty lines