Evas textblock: Fix _dict_hyphen_load could return an uninitialized pointer

Evas textblock: Fix _dict_hyphen_load could return an uninitialized pointer

Summary:
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

Change-Id: Id2ce93c6c55c39e7f5464963fb26dd715e87264e