Updated to not throw when returning a single item (this can just return null...

Updated to not throw when returning a single item (this can just return null as frames did) and added a test

.gitignore

@@ -3,3 +3,6 @@ target/
 .project
 .settings
 site
+.idea/
+ferma.iml
+

src/main/java/com/syncleus/ferma/framefactories/annotation/AdjacencyMethodHandler.java

@@ -362,7 +362,7 @@ public class AdjacencyMethodHandler extends AbstractMethodHandler {
                     default:
                         throw new IllegalStateException("Direction not recognized.");
                 }
-            }).next(VertexFrame.class);
+            }).nextOrDefault(VertexFrame.class, null);
         }
     }
 

src/test/java/com/syncleus/ferma/annotations/AdjacencyMethodHandlerTest.java

@@ -323,6 +323,26 @@ public class AdjacencyMethodHandlerTest {
         Assert.assertTrue(child instanceof GodExtended);
     }
 
+    @Test
+    public void testSetSonNull() {
+
+        GodGraphLoader.load(godGraph);
+
+        final FramedGraph framedGraph = new DelegatingFramedGraph(godGraph, TEST_TYPES);
+
+        final List<? extends God> gods = framedGraph.traverse(
+            input -> input.V().has("name", "jupiter")).toList(God.class);
+
+        final God father = gods.iterator().next();
+        Assert.assertTrue(father != null);
+        final VertexFrame fatherVertex = father;
+        Assert.assertEquals(fatherVertex.getProperty("name"), "jupiter");
+
+        father.setSon(null);
+        final God sonNull = father.getSon();
+        Assert.assertNull(sonNull);
+    }
+
     @Test
     public void testAddSonDefault() {