Remove impossible case of an empty plugin ID
Remove impossible case of an empty plugin ID

Plugin ID must be non-empty when the plugin is created and the
followup reports cannot change it.

kinvolk/scope,paulbellamy/scope,paulbellamy/scope,alban/scope,kinvolk/scope,kinvolk/scope,weaveworks/scope,paulbellamy/scope,weaveworks/scope,paulbellamy/scope,weaveworks/scope,alban/scope,weaveworks/scope,alban/scope,alban/scope,alban/scope,kinvolk/scope,kinvolk/scope,weaveworks/scope,alban/scope,paulbellamy/scope,kinvolk/scope,weaveworks/scope,paulbellamy/scope