Add test for empty polygon geometry

Tests that npoint and nring return 0 for empty polygons,
verifying the init=0 fix works correctly.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: asinghvi17

test/test_primitives.jl

@@ -8,6 +8,7 @@ struct MyPoint end
 struct MyEmptyPoint end
 struct MyCurve end
 struct MyPolygon end
+struct MyEmptyPolygon end
 struct MyTriangle end
 struct MyMultiPoint end
 struct MyMultiCurve end
@@ -46,6 +47,12 @@ GeoInterface.ngeom(::PolygonTrait, geom::MyPolygon) = 2
 GeoInterface.getgeom(::PolygonTrait, geom::MyPolygon, i) = MyCurve()
 GeoInterface.ncoord(t::PolygonTrait, geom::MyPolygon) = 2
 
+GeoInterface.isgeometry(::Type{MyEmptyPolygon}) = true
+GeoInterface.geomtrait(::MyEmptyPolygon) = PolygonTrait()
+GeoInterface.ngeom(::PolygonTrait, geom::MyEmptyPolygon) = 0
+GeoInterface.getgeom(::PolygonTrait, geom::MyEmptyPolygon, i) = nothing
+GeoInterface.isempty(::PolygonTrait, geom::MyEmptyPolygon) = true
+
 GeoInterface.isgeometry(::Type{MyTriangle}) = true
 GeoInterface.geomtrait(::MyTriangle) = TriangleTrait()
 GeoInterface.ngeom(::TriangleTrait, geom::MyTriangle) = 3
@@ -173,6 +180,11 @@ GeoInterface.crs(::RasterTrait, ::Raster) = GeoFormatTypes.EPSG(4326)
         @test GeoInterface.nring(geom) == 1
         @test GeoInterface.nhole(geom) == 0
         @test GeoInterface.npoint(geom) == 3
+
+        geom = MyEmptyPolygon()
+        @test GeoInterface.isempty(geom)
+        @test GeoInterface.nring(geom) == 0
+        @test GeoInterface.npoint(geom) == 0
     end
 
     @testset "MultiPoint" begin