Fix test for encrypted pool in _update_from_device.

library/blivet.py

@@ -824,7 +824,7 @@ def _update_from_device(self, param_name):
         """ Return True if param_name's value was retrieved from a looked-up device. """
         # We wouldn't have the pool device if the member devices weren't unlocked, so we do not
         # have to consider the case where the devices are unlocked like we do for volumes.
-        encrypted = all("luks" in d.type for d in self._device.parents)
+        encrypted = self._device.parents and all("luks" in d.type for d in self._device.parents)
         raid = len(self._device.parents) == 1 and hasattr(self._device.parents[0].raw_device, 'level')
         log.debug("BlivetPool._update_from_device: %s", self._device)