Early exit if there are no modifiers.

src/feature_placement.rs

@@ -392,10 +392,14 @@ fn filter_features_by_blocking_shapes(
     noise_cache: &mut NoiseCache,
 ) {
     let _span = info_span!("Filter features by blocking shapes").entered();
-    
+
     let shape_modifiers_in_tile = tile_to_modifier.shape.get(&tile);
     let spline_modifiers_in_tile = tile_to_modifier.splines.get(&tile);
 
+    if shape_modifiers_in_tile.is_none_or(|entries| entries.is_empty()) && spline_modifiers_in_tile.is_none_or(|entries| entries.is_empty()) {
+        return;
+    }
+
     feature_placements.iter_mut().enumerate().for_each(|(feature_group, placements)| {
         let feature_group = &terrain_features.feature_groups[feature_group];