diff binSearch should not fatal exit when data is equal

[Howie516]

Bug Report

Please answer these questions before submitting your issue. Thanks!

log:
[2022/06/11 04:00:58.280 +08:00] [FATAL] [diff.go:564] ["the isEqual1 and isEqual2 cannot be both true"] [stack="main.(*Diff).binSearch\n\t/Users/yunzhanghu1151/code/tidb-tools/sync_diff_inspector/diff.go:564\nmain.(*Diff).BinGenerate\n\t/Users/yunzhanghu1151/code/tidb-tools/sync_diff_inspector/diff.go:496\nmain.(*Diff).consume\n\t/Users/yunzhanghu1151/code/tidb-tools/sync_diff_inspector/diff.go:435\nmain.(*Diff).Equal.func2\n\t/Users/yunzhanghu1151/code/tidb-tools/sync_diff_inspector/diff.go:284\ngithub.com/pingcap/tidb-tools/sync_diff_inspector/utils.(*WorkerPool).Apply.func1\n\t/Users/yunzhanghu1151/code/tidb-tools/sync_diff_inspector/utils/utils.go:75"]

version: v5.4.1
diff.go 564 row
// If there is a count zero, we think the range is very small. if (!isEqual1 && !isEqual2) || (count1 == 0 || count2 == 0) { return tableRange, nil } else if !isEqual1 { c, err := df.binSearch(ctx, targetSource, tableRange1, count1, tableDiff, indexColumns) if err != nil { return nil, errors.Trace(err) } return c, nil } else if !isEqual2 { c, err := df.binSearch(ctx, targetSource, tableRange2, count2, tableDiff, indexColumns) if err != nil { return nil, errors.Trace(err) } return c, nil } else { // TODO: handle the error to foreground log.Fatal("the isEqual1 and isEqual2 cannot be both true") return nil, nil }

[Leavrth]

the same as #631
syncdiff need to set default snapshot if it is not set in config.