The installer for the ubuntu server doesn't handle partitioning on the RAID devices gracefully

1. Start installation of Ubuntu Server 16.04 on a system with no less than 2 disks.
2. Reach the Partition disk main menu
3. Create empty partition table to 2 (or more) disks
4. Create a RAID device over the 2 (or more) disks
5. The installer will show a single sub-item under the created RAID device. It looks like a partition already exists.
6. Select it to partition it.
If you select the RAID device, nothing happens.

Expected result:
The usual partitioning menu appears

Actual result
The usual partition usage menu appears (Use as:...)

Workaround
After step no.4 select "Undo changes to partitions".
Since the partition tables to the single storage devices have already been committed and nothing has been done yet to the md* devices, nothing will actually be lost. The storage device list will now show just the RAID devices with no sub-item.
Now you can select the RAID device to let the usual partitioning menu appear.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: debian-installer-launcher (not installed)
Uname: Linux 4.4.14-040414-lowlatency x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: KDE
Date: Mon Jul 4 12:06:18 2016
InstallationDate: Installed on 2016-04-22 (72 days ago)
InstallationMedia: Kubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
SourcePackage: debian-installer-launcher
UpgradeStatus: No upgrade log present (probably fresh install)