Reopen candidate list for symbols with down key

If these's only one candidate list available, down key
will use ChoiceFirstAvail to re-open the list, and turn
back to the first page. However, it doesn't work for
symbols, therefore we set the page number to 0 directly.

This should fix #127.
Merge pull request #135 from hiunnhue/sym_cand_list_reopen

Reopen candidate list for symbols with down key