#81 fix missing notFirst

Author: taowen

src/main/java/com/jsoniter/output/CodegenImplObject.java

@@ -41,7 +41,13 @@ public static CodegenResult genObject(ClassInfo classInfo) {
             if (noIndention) {
                 ctx.buffer('}');
             } else {
-                ctx.append("if (notFirst) { stream.writeObjectEnd(); } else { stream.write('}'); }");
+                if (notFirst == 1) { // definitely not first
+                    ctx.append("stream.writeObjectEnd();");
+                } else if (notFirst == 2) { // // maybe not first, previous field is omitNull
+                    ctx.append("if (notFirst) { stream.writeObjectEnd(); } else { stream.write('}'); }");
+                } else { // this is the first
+                    ctx.append("stream.write('}');");
+                }
             }
         } else {
             ctx.buffer("{}");

src/test/java/com/jsoniter/output/TestObject.java

@@ -321,4 +321,19 @@ public void test_indention_with_empty_object() {
                 .build();
         assertEquals("{}", JsonStream.serialize(config, new TestObject15()));
     }
+
+    public static class TestObject16 {
+        @JsonProperty(omitNull = false)
+        public Integer i;
+    }
+
+    public void test_missing_notFirst() {
+        Config cfg = JsoniterSpi.getCurrentConfig().copyBuilder()
+            .indentionStep(2)
+            .encodingMode(EncodingMode.DYNAMIC_MODE)
+            .build();
+        assertEquals("{\n" +
+                "  \"i\": null\n" +
+                "}", JsonStream.serialize(cfg, new TestObject16()));
+    }
 }