file: Initialize sort to order to default

If get_attributes_for_default_sort_type() returns FALSE,
nautilus_file_get_default_sort_type() will return garbage, as retval
will remain uninitialized. This commit initializes it by default to the
default GSettings value.

Fixes #794
3 jobs for master in 12 minutes and 42 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #169416
flatpak devel

00:11:44

9.3%
 
  Deploy
passed #169417
pages

00:00:58

passed pages:deploy

00:00:00