Erase and install ubiquity option leaving empty partitions

Steps to reproduce:

1. Install Ubuntu on the full disk on a VM
2. Install Ubuntu on the same machine and choose the option of automatic resizing
3. Install Ubuntu a third time and choose to Erase and install.

The partition table shows 2 empty entries:
I get a warning:
Warning: extended partition does not start at a cylinder boundary.
DOS and Linux will interpret the contents differently.

And this is the stdout:
Disk /dev/sda: 1614 cylinders, 255 heads, 63 sectors/track
Units = cylinders of 8225280 bytes, blocks of 1024 bytes, counting from 0

   Device Boot Start End #cyls #blocks Id System
/dev/sda1 * 0+ 1484- 1485- 11921408 83 Linux
/dev/sda2 1484+ 1614- 131- 1046529 5 Extended
/dev/sda3 0 - 0 0 0 Empty
/dev/sda4 0 - 0 0 0 Empty
/dev/sda5 1484+ 1614- 131- 1046528 82 Linux swap / Solaris

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: ubiquity (not installed)
ProcVersionSignature: Ubuntu 3.8.0-19.29-generic 3.8.8
Uname: Linux 3.8.0-19-generic i686
ApportVersion: 2.9.2-0ubuntu8
Architecture: i386
Date: Wed Apr 24 09:43:42 2013
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash -- maybe-ubiquity
InstallationDate: Installed on 2013-04-24 (0 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release i386 (20130423.1)
MarkForUpload: True
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)