can not open a bot if manifest url is invalid

[hibrenda]

• create a consumer bot
• create a skill connection and skillbot hosted in local as following
  
• shut down composer
• restart composer
• open consumer bot will hit following error
• bot can not be opened

Workaround: start the skillbot and make sure in port 3979.

[boydc2014]

The expected behavior should be this error should not block opening.

So, the proper treatment in UX, to me, is to display an invalid status in skills page when user have an invalid entry, and filter out invalid entry to form for selection, that's probably good enough.

[cwhitten]

#3050