add testcase for issue #569

src/test/java/com/alibaba/json/bvt/bug/Issue569_1.java

+package com.alibaba.json.bvt.bug;
+
+import com.alibaba.fastjson.JSON;
+import com.alibaba.fastjson.TypeReference;
+import junit.framework.TestCase;
+
+public class Issue569_1 extends TestCase {
+    public void test_for_issue() throws Exception {
+        String json = "{\"result\":{}}";
+        InterfaceResult<Value> result = JSON.parseObject(json, new TypeReference<InterfaceResult<Value>>() {});
+        assertNotNull(result.getResult());
+        assertEquals(Value.class, result.getResult().getClass());
+    }
+
+    public static class BaseInterfaceResult {
+
+    }
+
+    public static class InterfaceResult<T> extends BaseInterfaceResult
+    {
+        public T getResult() {
+            return result;
+        }
+
+        public void setResult(T result) {
+            this.result = result;
+        }
+
+        private T result;
+    }
+
+    public static class Value {
+
+    }
+}