add special empty map

I am deeply unhappy about ugly disclaimer handling though right now I have no good ideas how to provide nicer display

app/map_styles/polygon.xml

@@ -308,6 +308,8 @@
             <LineSymbolizer stroke="#888" stroke-width="3.0"/>
         </Rule>
     </Style>
+    <Style name="empty_map">
+    </Style>
     <Style name="conservation_area">
         <Rule>
             <PolygonSymbolizer fill="#73ebaf" />

app/src/frontend/config/category-maps-config.ts

@@ -270,6 +270,15 @@ export const categoryMapsConfig: {[key in Category]: CategoryMapDefinition[]} =
                     { color: '#8500d4', text: 'In Archaeological Priority Area'},
                 ]
             },
+        },
+        {
+            mapStyle: 'empty_map',
+            legend: {
+                title: 'Empty map',
+                disclaimer: 'This is an empty map to see overlays without distraction.',
+                elements: [
+                ]
+            },
         }
     ],
     [Category.Sustainability]: [{

app/src/frontend/config/tileserver-config.ts

@@ -17,6 +17,7 @@ export type BuildingMapTileset = 'date_year' |
     'planning_applications_status' |
     'planning_applications_status_secretary_of_state' |
     'planning_combined' |
+    'empty_map' |
     'sust_dec' |
     'building_attachment_form' |
     'landuse' |

app/src/frontend/map/legend.tsx

@@ -81,7 +81,7 @@ export const Legend : FC<LegendProps> = ({
             }
             {
                 elements.length === 0 ?
-                    <p className="data-intro">Coming soon…</p> :
+                    ( disclaimer ? <ul className={collapseList ? 'collapse data-legend' : 'data-legend'} ><p className='legend-disclaimer'>{disclaimer}</p></ul> : <p className="data-intro">Coming soon…</p>) :
                     <ul className={collapseList ? 'collapse data-legend' : 'data-legend'} >
                         {
                             disclaimer && <p className='legend-disclaimer'>{disclaimer}</p>

app/src/tiles/dataDefinition.ts

@@ -193,6 +193,13 @@ const LAYER_QUERIES = {
             OR planning_heritage_at_risk_url <> ''
             OR planning_in_apa_url <> ''
             `,
+    empty_map: `
+        SELECT
+            geometry_id
+        FROM
+            buildings
+        WHERE
+            sust_dec IS NOT NULL`,
         conservation_area: `
         SELECT
             geometry_id