There is also a problem in html-importer.php on lines 640 and 641.
The are:
if ( !is_wp_error( $previous_import ) && !empty( $previous_import )
&& $previous_import->post_title = $my_post['post_title'] ) {
They should be:
if ( !is_wp_error( $previous_import ) && !empty( $previous_import )
&& $previous_import->post_title == $my_post['post_title'] ) {
That is on line 641 the operator should be == (equals) instead of = (assignment).