The scroll buffer is not released when tsm_screen is destroyed in tsm_screen_unref.

diff --git a/src/tsm/tsm-screen.c b/src/tsm/tsm-screen.c
index 2004d9f..575044a 100644
--- a/src/tsm/tsm-screen.c
+++ b/src/tsm/tsm-screen.c
@@ -536,6 +536,7 @@ void tsm_screen_unref(struct tsm_screen *con)
        free(con->alt_lines);
        free(con->tab_ruler);
        tsm_symbol_table_unref(con->sym_table);
+       tsm_screen_clear_sb(con);
        free(con);
 }