Remove unneeded "else null" in conditions (#732)

Minor code cleanup:
SQL already returns NULL in the "WHEN" condition
if it is not matched by any of the cases.

Co-authored-by: Eva Jelinkova <evka.jelinkova@gmail.com>

layers/poi/layer.sql

@@ -21,7 +21,7 @@ RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text, name_de
         agg_stop,
         NULLIF(layer, 0) AS layer,
         "level",
-        CASE WHEN indoor=TRUE THEN 1 ELSE NULL END as indoor,
+        CASE WHEN indoor=TRUE THEN 1 END as indoor,
         row_number() OVER (
             PARTITION BY LabelGrid(geometry, 100 * pixel_width)
             ORDER BY CASE WHEN name = '' THEN 2000 ELSE poi_class_rank(poi_class(subclass, mapping_key)) END ASC

layers/poi/poi_stop_agg.sql

@@ -3,8 +3,7 @@ CREATE MATERIALIZED VIEW osm_poi_stop_centroid AS (
   SELECT
       uic_ref,
       count(*) as count,
-			CASE WHEN count(*) > 2 THEN ST_Centroid(ST_UNION(geometry))
-			ELSE NULL END AS centroid
+      CASE WHEN count(*) > 2 THEN ST_Centroid(ST_UNION(geometry)) END AS centroid
   FROM osm_poi_point
 	WHERE
 		nullif(uic_ref, '') IS NOT NULL

layers/poi/update_poi_point.sql

@@ -27,7 +27,6 @@ BEGIN
   SET agg_stop = CASE
       WHEN p.subclass IN ('bus_stop', 'bus_station', 'tram_stop', 'subway')
         THEN 1
-      ELSE NULL
   END;
 
   UPDATE osm_poi_point p
@@ -36,7 +35,6 @@ BEGIN
         WHEN p.subclass IN ('bus_stop', 'bus_station', 'tram_stop', 'subway')
             AND r.rk IS NULL OR r.rk = 1
           THEN 1
-        ELSE NULL
       END)
     FROM osm_poi_stop_rank r
     WHERE p.osm_id = r.osm_id