Evas textblock: Fix _dict_hyphen_load could return an uninitialized pointer
If there are hyph_*.dic files except for requested language,
"dict" pointer could be return without initialized. It doesn't make any
warning messages when it is compiled. Normally, it is NULL implicitly.
But, it is good to set NULL explicitly for understanding code.
Test Plan: N/A
Reviewers: herdsman, tasn, woohyun
Subscribers: cedric, jpeg
Differential Revision: https://phab.enlightenment.org/D3674