device: Fix crash attempting to read Sets property

device: Fix crash attempting to read Sets property

The following set can be observed when a sirk is exists but it is
encrypted leading to info->set to not be set:

Invalid read of size 8
   at 0x1ACDF0: append_set (device.c:1662)
   by 0x1FFEFFF7DF: ???
   by 0x1D4461: queue_foreach (queue.c:207)
   by 0x1AC8DE: dev_property_get_set (device.c:1700)
   by 0x1CF3E2: append_property (object.c:498)
   by 0x1CFA91: append_properties (object.c:527)
   by 0x1CFAFD: append_interface (object.c:542)
   by 0x48D7CEF: g_slist_foreach (gslist.c:887)
   by 0x1CF5A7: append_interfaces (object.c:1104)
   by 0x1CF5A7: append_object (object.c:1119)
   by 0x48D7CEF: g_slist_foreach (gslist.c:887)
   by 0x1CF5D0: append_object (object.c:1122)
   by 0x48D7CEF: g_slist_foreach (gslist.c:887)
 Address 0x8 is not stack'd, malloc'd or (recently) free'd