Synchronize zero sized files (fixes #44)

model/blocks.go

@@ -37,6 +37,15 @@ func Blocks(r io.Reader, blocksize int) ([]Block, error) {
 		offset += int64(n)
 	}
 
+	if len(blocks) == 0 {
+		// Empty file
+		blocks = append(blocks, Block{
+			Offset: 0,
+			Size:   0,
+			Hash:   []uint8{0xe3, 0xb0, 0xc4, 0x42, 0x98, 0xfc, 0x1c, 0x14, 0x9a, 0xfb, 0xf4, 0xc8, 0x99, 0x6f, 0xb9, 0x24, 0x27, 0xae, 0x41, 0xe4, 0x64, 0x9b, 0x93, 0x4c, 0xa4, 0x95, 0x99, 0x1b, 0x78, 0x52, 0xb8, 0x55},
+		})
+	}
+
 	return blocks, nil
 }