bindinfo: fix panic when load invalid sqls

[alivxxx]

What problem does this PR solve?

When sqls in the bind_info table is not valid, it will panic in Update.

What is changed and how it works?

It panics in

		hash, meta, err := h.newBindMeta(newBindRecord(row))
		// Update lastUpdateTime to the newest one.
		if meta.UpdateTime.Compare(h.lastUpdateTime) > 0 {
			h.lastUpdateTime = meta.UpdateTime
		}

The invalid sql would cause error in newBindMeta, and the meta is nil, so it cause panic in following lines. This PR does not fixes it by check err first because we need to update the lastUpdateTime to avoid fail in next Update.

Check List

Tests

• Unit test

Code changes

• Has exported function/method change

Side effects

• None

Related changes

• None

Release note

• fix panic when load invalid bind records into cache

[lzmhhh123]

LGTM

[eurekaka]

LGTM

[sre-bot]

/run-all-tests

[zz-jason]

do we have this bug in master branch?

[alivxxx]

@zz-jason No