Don't crash when a free region is too small for an aligned partition.
Don't crash when a free region is too small for an aligned partition.

Resolves: rhbz#1167292

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