Fix potential traceback in devicetree.populate. (#1055523)
Fix potential traceback in devicetree.populate. (#1055523)

Traceback introduced by commit a11f3a8795ed from master.

vpodzime/blivet,vpodzime/blivet,rhinstaller/blivet,AdamWill/blivet,dwlehman/blivet,jkonecny12/blivet,vojtechtrefny/blivet,rhinstaller/blivet,AdamWill/blivet,dwlehman/blivet,rvykydal/blivet,rvykydal/blivet,vojtechtrefny/blivet,jkonecny12/blivet