Inaccessible panels when setting two panels to the same orientation

[monstrous]

1) Version-information
Linux Mint: LMDE 201204 (patched today on 2012/08/11 to the latest versions), 32 Bit
Mate: 1.2.0

2) Problem and reproduction
After adding a second panel on Mate that has been placed on "top" orientation and editing the settings of the standard-panel to be also displayed on the top, both panels kind of crash.

3) What happened
After restarting X, restarting MDM and/or restarting the complete system the fresh added panel starts to blink while the second cannot be seen. None of the panels can be right-clicked to edit the settings. The desktop is kind of unusable.

4) Expectation
- There should be an errormessage saying that two panels with the same orientation is not possible
- Or the option "top" (or any other chosen option) should not be usable if another panel uses its orientation already
- Or - if two panels on one orientation are possible - one of them should be clickable to change its settings.

5) The problem happens always.

Quick fix: Edit ".mateconf/apps/panel/toplevels/panel_0/%mateconf.xml" and change the orientation from "top" to "bottom":

*snip*
<mateconf>
        <entry name="orientation" mtime="1344714350" type="string">
                <stringvalue>bottom</stringvalue>
        </entry>
</mateconf>
*snip*

[bi-user (bi-user)]

same panel problem every mint mate after 13, ubuntu mate 16.04, point linux 3.2. no problem for me on ubuntu 15.10 however.