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/transportation/class.sql

@@ -3,7 +3,6 @@ CREATE OR REPLACE FUNCTION brunnel(is_bridge BOOL, is_tunnel BOOL, is_ford BOOL)
         WHEN is_bridge THEN 'bridge'
         WHEN is_tunnel THEN 'tunnel'
         WHEN is_ford THEN 'ford'
-        ELSE NULL
     END;
 $$ LANGUAGE SQL IMMUTABLE STRICT;
 
@@ -24,9 +23,7 @@ CREATE OR REPLACE FUNCTION highway_class(highway TEXT, public_transport TEXT, co
           WHEN construction = 'service' THEN 'service_construction'
           WHEN construction = 'track' THEN 'track_construction'
           WHEN construction = 'raceway' THEN 'raceway_construction'
-          ELSE NULL
         END
-        ELSE NULL
     END;
 $$ LANGUAGE SQL IMMUTABLE;
 
@@ -36,7 +33,6 @@ CREATE OR REPLACE FUNCTION railway_class(railway TEXT) RETURNS TEXT AS $$
     SELECT CASE
         WHEN railway IN ('rail', 'narrow_gauge', 'preserved', 'funicular') THEN 'rail'
         WHEN railway IN ('subway', 'light_rail', 'monorail', 'tram') THEN 'transit'
-        ELSE NULL
     END;
 $$ LANGUAGE SQL IMMUTABLE STRICT;
 
@@ -45,7 +41,6 @@ $$ LANGUAGE SQL IMMUTABLE STRICT;
 CREATE OR REPLACE FUNCTION service_value(service TEXT) RETURNS TEXT AS $$
     SELECT CASE
         WHEN service IN ('spur', 'yard', 'siding', 'crossover', 'driveway', 'alley', 'parking_aisle') THEN service
-        ELSE NULL
     END;
 $$ LANGUAGE SQL IMMUTABLE STRICT;
 
@@ -55,6 +50,5 @@ CREATE OR REPLACE FUNCTION surface_value(surface TEXT) RETURNS TEXT AS $$
     SELECT CASE
         WHEN surface IN ('paved', 'asphalt', 'cobblestone', 'concrete', 'concrete:lanes', 'concrete:plates', 'metal', 'paving_stones', 'sett', 'unhewn_cobblestone', 'wood') THEN 'paved'
         WHEN surface IN ('unpaved', 'compacted', 'dirt', 'earth', 'fine_gravel', 'grass', 'grass_paver', 'gravel', 'gravel_turf', 'ground', 'ice', 'mud', 'pebblestone', 'salt', 'sand', 'snow', 'woodchips') THEN 'unpaved'
-        ELSE NULL
     END;
 $$ LANGUAGE SQL IMMUTABLE STRICT;

layers/transportation/layer.sql

@@ -23,7 +23,6 @@ indoor INT, bicycle TEXT, foot TEXT, horse TEXT, mtb_scale TEXT, surface TEXT) A
             WHEN (highway IS NOT NULL OR public_transport IS NOT NULL)
                 AND highway_class(highway, public_transport, construction) = 'path'
                 THEN COALESCE(NULLIF(public_transport, ''), highway)
-            ELSE NULL
         END AS subclass,
         -- All links are considered as ramps as well
         CASE WHEN highway_is_link(highway) OR highway = 'steps'
@@ -33,7 +32,7 @@ indoor INT, bicycle TEXT, foot TEXT, horse TEXT, mtb_scale TEXT, surface TEXT) A
         NULLIF(service, '') AS service,
         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,
         NULLIF(bicycle, '') AS bicycle,
         NULLIF(foot, '') AS foot,
         NULLIF(horse, '') AS horse,
@@ -157,12 +156,8 @@ indoor INT, bicycle TEXT, foot TEXT, horse TEXT, mtb_scale TEXT, surface TEXT) A
             public_transport, service_value(service) AS service,
             is_bridge, is_tunnel, is_ford, is_ramp, is_oneway, man_made,
             layer,
-            CASE WHEN highway IN ('footway', 'steps') THEN "level"
-                ELSE NULL::int
-            END AS "level",
-            CASE WHEN highway IN ('footway', 'steps') THEN indoor
-                ELSE NULL::boolean
-            END AS indoor,
+            CASE WHEN highway IN ('footway', 'steps') THEN "level" END AS "level",
+            CASE WHEN highway IN ('footway', 'steps') THEN indoor END AS indoor,
             bicycle, foot, horse, mtb_scale,
             surface_value(surface) AS "surface",
             z_order