check float will return error.When float data has 0 value on source or on target

[erwadba]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?
   If possible, provide a recipe for reproducing the error.
   source tidb

mysql> create table f(id int primary key,f float);
mysql> insert into f values(1,2),(2,4.5),(3,0);

target tidb

mysql> create table f(id int primary key,f float);
mysql> insert into f values(1,0),(2,0),(3,0);

2. What did you expect to see?
   no error

3. What did you see instead?

convert , 4.5 to float failed, err1: strconv.ParseFloat: parsing "": invalid syntax, err2: error occured in a.f

4. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?
   v6.5.0
5. which tool are you using?
   sync_diff_inspector
6. what versionof tool are you using (pump -V or tidb-lightning -V or syncer -V)?