Opening the 'preview' link in the list of channels breaks when different channels use different host names

When a site has multiple channels that are accessible over different host names, clicking the 'preview' link of a channel in the channel list breaks when the second channel is previewed. This second preview then still shows the preview of the site clicked first.

The bug is also visible in Firebug / Chrome Dev Tools when multiple channels use the same host: the REST call to set the rendering host before opening the preview URL (see the steps below) then returns a 404.

Steps to reproduce:
1. open the Net panel in Firebug or the Network section in Chrome's Dev Tools
2. log in to the GoGreen CMS as admin
3. navigate to the list of channels
4. click on 'Preview' of the English Website

Notice in Firebug/Chrome that a REST call is done first to /site/_rp/cafebabe-cafe-babe-cafe-babecafebabe./composermode

5. select the tab with the CMS again
6. click on 'Preview' of the French Website
7. check the REST call in Firebug/Chrome

Expected behavior: the second REST call to /site/_rp/cafebabe-cafe-babe-cafe-babecafebabe./composermode returns 200 (OK)
Actual behavior: the second REST call to /site/_rp/cafebabe-cafe-babe-cafe-babecafebabe./composermode returns 404 (Not Found)

In this scenario the preview is still visible since the channels the same host but different mounts. However, when this scenario is repeated for two channels using differents hostnames (e.g. mysite.com and mysite.fr), step 7 would still show the preview of the English Website instead of the French website. This is because the REST call that sets the new host (mysite.fr) fails, and mysite.com would still be used.

As a workaround, you can first open the channel in the template composer (by clicking the channels name). If you then go back to the channel list and click 'Preview', the correct preview is opened.