virtio-blkd: Do not crash when the disk is empty

storage/virtio-blkd/src/main.rs

@@ -1,8 +1,6 @@
 #![deny(trivial_numeric_casts, unused_allocation)]
 #![feature(int_roundings)]
 
-// TODO(andypython): driver panic with an empty disk.
-
 use std::fs::File;
 use std::io::{Read, Write};
 use std::os::fd::{FromRawFd, RawFd};

storage/virtio-blkd/src/scheme.rs

@@ -184,10 +184,10 @@ impl<'a> DiskScheme<'a> {
         };
 
         let part_table = partitionlib::get_partitions(&mut shim, LogicalBlockSize::Lb512)
-            .unwrap()
-            .expect("virtiod: no partitions found");
+            .ok()
+            .flatten();
 
-        this.part_table = Some(part_table);
+        this.part_table = part_table;
         this
     }
 }