Ondrej Holy authored Dec 10, 2020 and Philip Withnall committed Dec 11, 2020

NULL is valid return value for the g_unix_mount_get_options function
because mount options are currently provided only by libmount implementation.
However, the gio tool passes the returned value to the g_strescape function
without checking, which produces the following critical warning:
GLib-CRITICAL **: 13:47:15.294: g_strescape: assertion 'source != NULL' failed

Let's add the missing check to prevent the critical warnings.