Small conversation api changes

What does this MR do?

The conversation API currently returns conversations like this:

When the conversation has a name:

{
  "conversation": {
    "name": "nice conversation name"
  },
 ... other stuff
}

When it does not have a name:

{
  "conversation": [],
 ... other stuff
}

This fucks with the android app as it can't cope with it being an object in one case, and an array in the other case.

These changes make it so:

When the conversation has a name:

{
  "name": "nice conversation name",
 ... other stuff
}

When it does not have a name:

{
  "name": null,
 ... other stuff
}

How confident are you it won't break things if deployed?

I think I need to fix the desktop js first... Fixed it!

Should be good to go!

Links to related issues

Checklist

• added a test, or explain why one is not needed/possible... aaaaaaaaaaah
• no unrelated changes
• asked someone for a code review
• joined #foodsharing-beta channel at https://slackin.yunity.org
• added an entry to CHANGELOG.md (description, merge request link, username(s))