fix(migrations): Correct NULL to empty string in SQL insert

[pingsutw]

Tracking issue

NA

Why are the changes needed?

value is a primary key in the execution_tag table, so we can't insert a NULL value into that column.

What changes were proposed in this pull request?

Insert an empty string instead.

How was this patch tested?

local sandbox

Setup process

Screenshots

Check all the applicable boxes

• [x] I updated the documentation accordingly.
• [x] All new and existing tests passed.
• [x] All commits are signed-off.

Related PRs

NA

Docs link

NA

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 60.99%. Comparing base (59e18d1) to head (1090100).

Files	Patch %	Lines
flyteadmin/pkg/repositories/config/migrations.go	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #5482 +/- ## ========================================== + Coverage 60.97% 60.99% +0.01% ========================================== Files 793 793 Lines 51350 51350 ========================================== + Hits 31312 31319 +7 + Misses 17152 17145 -7 Partials 2886 2886 ``` | [Flag](https://app.codecov.io/gh/flyteorg/flyte/pull/5482/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | Coverage Δ | | |---|---|---| | [unittests-datacatalog](https://app.codecov.io/gh/flyteorg/flyte/pull/5482/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `69.31% <ø> (ø)` | | | [unittests-flyteadmin](https://app.codecov.io/gh/flyteorg/flyte/pull/5482/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `58.70% <0.00%> (+0.04%)` | :arrow_up: | | [unittests-flytecopilot](https://app.codecov.io/gh/flyteorg/flyte/pull/5482/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `17.79% <ø> (ø)` | | | [unittests-flytectl](https://app.codecov.io/gh/flyteorg/flyte/pull/5482/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `67.97% <ø> (ø)` | | | [unittests-flyteidl](https://app.codecov.io/gh/flyteorg/flyte/pull/5482/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `79.04% <ø> (ø)` | | | [unittests-flyteplugins](https://app.codecov.io/gh/flyteorg/flyte/pull/5482/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `61.84% <ø> (ø)` | | | [unittests-flytepropeller](https://app.codecov.io/gh/flyteorg/flyte/pull/5482/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `57.30% <ø> (ø)` | | | [unittests-flytestdlib](https://app.codecov.io/gh/flyteorg/flyte/pull/5482/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg) | `65.82% <ø> (+0.02%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flyteorg#carryforward-flags-in-the-pull-request-comment) to find out more.

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