fix lookup crash when has nullable cols

[critical27]

What type of PR is this?

• bug
• feature
• enhancement

What problem(s) does this PR solve?

Issue(s) number:

#4230

Description:

The main problem has two parts:

1. The indexNullable_ in IndexScanNode is not initialized correctly.
2. In IndexScanNode, the offset of nullable bits is not calculated correctly.

How do you solve it?

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

Check if there is an nullable property when build plan.

Checklist:

Tests:

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

Affects:

• 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

Release notes:

Please confirm whether to be reflected in release notes and how to describe:
Fix storage may crash when lookup index with nullable property.