Repair some problems in query_concurrently mode

[cangfengzhs]

1. Null pointer exception in IndexTopNNode

2. The expression in IndexSelectionNode is incorrectly shared

3. The IndexTopNNode is incorrectly constructed, resulting in incorrect data

What type of PR is this?

• bug
• feature
• enhancement

What problem(s) does this PR solve?

Issue(s) number:

Description:

How do you solve it?

Special notes for your reviewer, ex. impact of this fix, design document, etc:

Checklist:

Tests:

• Unit test(positive and negative cases)
• Function test
• Performance test
• N/A

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• Documentation affected (Please add the label if documentation needs to be modified.)
• Incompatibility (If it breaks the compatibility, please describe it and add the label.）
• If it's needed to cherry-pick (If cherry-pick to some branches is required, please label the destination version(s).)
• Performance impacted: Consumes more CPU/Memory

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ex. Fixed the bug .....