Don't return null buffer polygon (#243)

Author: stolstov

src/main/java/com/esri/core/geometry/Bufferer.java

@@ -576,6 +576,9 @@ private Geometry bufferPolygon_() {
 		generateCircleTemplate_();
 		m_geometry = simplify.execute(m_geometry, null, false,
 				m_progress_tracker);
+		if(m_geometry.isEmpty()) {
+			return m_geometry;
+		}
 
 		if (m_distance < 0) {
 			Polygon poly = (Polygon) (m_geometry);
@@ -600,7 +603,12 @@ private Geometry bufferPolygon_() {
 					.getInstance().getOperator(Operator.Type.Union)).execute(
 					cursor, m_spatialReference, m_progress_tracker);
 			Geometry result = union_cursor.next();
-			return result;
+			if (result != null) {
+				return result;
+			} else {
+				//never return empty.
+				return new Polygon(m_geometry.getDescription());
+			}
 		}
 	}
 

src/test/java/com/esri/core/geometry/TestBuffer.java

@@ -27,6 +27,8 @@
 import junit.framework.TestCase;
 import org.junit.Test;
 
+import com.esri.core.geometry.ogc.OGCGeometry;
+
 public class TestBuffer extends TestCase {
 	@Override
 	protected void setUp() throws Exception {
@@ -389,4 +391,27 @@ public void testBufferPolygon() {
 			assertTrue(simplify.isSimpleAsFeature(result, sr, null));
 		}
 	}
+	
+	@Test
+	public static void testTinyBufferOfPoint() {
+		{
+			Geometry result1 = OperatorBuffer.local().execute(new Point(0, 0), SpatialReference.create(4326), 1e-9, null);
+			assertTrue(result1 != null);
+			assertTrue(result1.isEmpty());
+			Geometry geom1 = OperatorImportFromWkt.local().execute(0, Geometry.Type.Unknown, "POLYGON ((177.0 64.0, 177.0000000001 64.0, 177.0000000001 64.0000000001, 177.0 64.0000000001, 177.0 64.0))", null);
+			Geometry result2 = OperatorBuffer.local().execute(geom1, SpatialReference.create(4326), 0.01, null);
+			assertTrue(result2 != null);
+			assertTrue(result2.isEmpty());
+			
+		}
+		
+		{
+			OGCGeometry p = OGCGeometry.fromText(
+					"POLYGON ((177.0 64.0, 177.0000000001 64.0, 177.0000000001 64.0000000001, 177.0 64.0000000001, 177.0 64.0))");
+			OGCGeometry buffered = p.buffer(0.01);
+			assertTrue(buffered != null);
+		}
+		
+		
+	}		
 }