Fix the nil pointer panic caused by empty MetaCache in HybridSearch

[hedane]

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: hedane To complete the pull request process, please assign sunby after the PR has been reviewed. You can assign the PR to them by writing /assign @sunby in a comment when ready.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment Approvers can cancel approval by writing /approve cancel in a comment

[sre-ci-robot]

Welcome @hedane! It looks like this is your first PR to milvus-io/milvus-sdk-go 🎉

[congqixia]

@hedane thanks for the fix and contribution! could you please fix the DCO check so that we could merge you patch?

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: congqixia, hedane

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• ~~OWNERS~~ [congqixia]

Approvers can indicate their approval by writing /approve in a comment Approvers can cancel approval by writing /approve cancel in a comment

[congqixia]

manual add label for main repo behavior update

[congqixia]

/kind bug