An empty category is not shown when in focus

Given a a topology provider which supports searching for categories (e.g. Enhanced Linkd) the following issue is present:

• Clear the focus (No focus defined window appears)
• Search for a category which does not have any vertices (nodes) assigned
• The vertex is in focus but the "no focus defined window" is still present
• collapse the vertex -> The "no focus defined window" is still present

From my point of view the "no focus defined window" should not be present if:

• A collapsible Vertex is in focus (even if it does not contain any vertices)
• A collapsible vertex should be shown when collapsed, even if it does not contain any vertices