Fix map extra spawning in Backrooms

The id used by the terrain was incorrect, but more importantly, map
extras were checked against the 'default' region, not the default
region.

Change the id for the map extra collection to match that used by the
terrains, and check the default region, not the region with the id
default for map extras.

Author: ehughsbaird

data/mods/Backrooms/region_settings/region_settings/regional_map_settings.json

@@ -13,7 +13,7 @@
   },
   {
     "type": "map_extra_collection",
-    "id": "backrooms_backrooms",
+    "id": "backrooms",
     "chance": 30,
     "extras": [
       [ "mx_teleporter_node", 5000 ],
@@ -41,7 +41,7 @@
     "type": "region_settings_map_extras",
     "id": "default_backrooms",
     "copy-from": "default",
-    "extras": [ "backrooms_backrooms" ]
+    "extras": [ "backrooms" ]
   },
   {
     "type": "region_terrain_furniture",

src/mapgen.cpp

@@ -917,8 +917,7 @@ void map::generate( const tripoint_abs_omt &p, const time_point &when, bool save
 
         if( any_missing || !save_results ) {
             const region_settings_map_extras settings_mx =
-                region_settings_default->get_settings_map_extras();
-            // At some point, we should add region information so we can grab the appropriate extras
+                region_settings_id( get_option<std::string>( "DEFAULT_REGION" ) )->get_settings_map_extras();
             auto mx_iter = settings_mx.extras.find( map_extra_collection_id( terrain_type->get_extras() ) );
             if( mx_iter != settings_mx.extras.end() ) {
                 const map_extra_collection &this_ex = **mx_iter;