handle edge case of no impact layer

[gubuntu]

Problem

In the INGC demo I did a quick analysis of EQ on energy infrastructure in a few districts. It turned out that only one energy installation fell into my analysis area and it was not affected. Therefore,

• no impact layer was generated
• a GeoNode 'layer' was generated with no content and no thumbnail
• the impact report was empty (no map)

proposed solution

if nothing is affected, just notify the user and do not generate nor try to publish impact layers or reports?