Unconsumed '}' in (*traverser).decodeObject() causes entries loss after nested empty object

[zhongxinghong]

The #630 lost self.parser.p++ for empty object in (*traverser).decodeObject(). The TwitterJSON doesn't contain pattern like {..., "k": {}, ...} so this problem was not detected by unit tests.

Test case: {"v0": 0, "m0": {}, "v1": 1, "a0": [], "v2": 2}
Output:

=== RUN   TestVisitor_NodeDiff/issue_case02
    visitor_test.go:243: 
                Error Trace:    /Users/bytedance/go/src/github.com/bytedance/sonic/ast/visitor_test.go:243
                                                        /Users/bytedance/go/src/github.com/bytedance/sonic/ast/visitor.go:304
                                                        /Users/bytedance/go/src/github.com/bytedance/sonic/ast/visitor.go:167
                                                        /Users/bytedance/go/src/github.com/bytedance/sonic/ast/visitor.go:132
                                                        /Users/bytedance/go/src/github.com/bytedance/sonic/ast/visitor_test.go:318
                                                        /Users/bytedance/go/src/github.com/bytedance/sonic/ast/visitor_test.go:342
                Error:          Not equal: 
                                expected: []string{"a0", "m0", "v0", "v1", "v2"}
                                actual  : []string{"m0", "v0"}
                            
                                Diff:
                                --- Expected
                                +++ Actual
                                @@ -1,7 +1,4 @@
                                -([]string) (len=5) {
                                - (string) (len=2) "a0",
                                +([]string) (len=2) {
                                  (string) (len=2) "m0",
                                - (string) (len=2) "v0",
                                - (string) (len=2) "v1",
                                - (string) (len=2) "v2"
                                + (string) (len=2) "v0"
                                 }
                Test:           TestVisitor_NodeDiff/issue_case02