edje_cc: fix a memory leak issue when edje_cc writes images

edje_cc: fix a memory leak issue when edje_cc writes images

Summary:
If there is no given pathes for image files as parameter of edje_cc,
"img_dirs" will be NULL. Then, a local variable "load_err" is always
EVAS_LOAD_ERROR_NONE. Because of this, the "if" condition just after
EINA_LIST_FOREACH() will fail. It causes memory leak from "iw".
@fix

Test Plan: N/A

Reviewers: raster, cedric, jpeg, woohyun

Differential Revision: https://phab.enlightenment.org/D5285

Signed-off-by: Cedric Bail <cedric@osg.samsung.com>