options_wallpaper: Check retrun value of edje_object_file_set

edje_object_file_set can fail. Better check for the return value and act
accordingly.

CID 1147527
utils: Check retrun value of edje_object_file_set

In this case it not really useful as the functions returns void and
this is the last instruction anyway. Still better to have this in to
set good examples in the code.

CID 1100661
tyls: Make sure we never divide by zero

Avoid the case where cols is 0 and we divide through it.

CID 1100655