sync load cannot stop to retry when to load empty stats

[hawkingrei]

Bug Report

Please answer these questions before submitting your issue. Thanks!

sync load cannot stop to retry when to load empty stats

1. Minimal reproduce step (Required)

2. What did you expect to see? (Required)

cannot always report this log

3. What did you see instead (Required)

4. What is your TiDB version? (Required)