fix(menu): add if statement for missing slots

[najikahalsema]

Description

If the MenuItem's children don't have a contentSlot or iconSlot, we shouldn't do the work in get itemChildren(), because it's throwing an error when trying to map assignedElements for something that is null.

Related issue(s)

fixes #3626 (hopefully)

Motivation and context

Erroring in webcomponents.dev (example)

How has this been tested?

• Test case 1
  1. Go here
  2. Do this
• Test case 2
  1. Go here
  2. Do this

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (minor updates related to the tooling or maintenance of the repository, does not impact compiled assets)

Checklist

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• If my change required a change to the documentation, I have updated the documentation in this pull request.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have reviewed at the Accessibility Practices for this feature, see: Aria Practices

Best practices

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[github-actions]

Branch Preview

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Visual regression test results

When a visual regression test fails (or has previously failed while working on this branch), its results can be found in the following URLs:

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[github-actions]

Tachometer results

Chrome

action-menu permalink

Version	Bytes	Avg Time	vs remote	vs branch
npm latest	639 kB	303.62ms - 311.31ms	-	unsure 🔍 -1% - +2% -1.65ms - +7.42ms
branch	625 kB	302.17ms - 306.98ms	unsure 🔍 -2% - +1% -7.42ms - +1.65ms	-

menu permalink

Version	Bytes	Avg Time	vs remote	vs branch
npm latest	461 kB	450.70ms - 458.37ms	-	slower ❌ 2% - 4% 6.92ms - 17.04ms
branch	448 kB	439.26ms - 445.86ms	faster ✔ 2% - 4% 6.92ms - 17.04ms	-

picker permalink

Version	Bytes	Avg Time	vs remote	vs branch
npm latest	505 kB	990.15ms - 1011.95ms	-	unsure 🔍 -1% - +2% -13.74ms - +16.20ms
branch	491 kB	989.56ms - 1010.08ms	unsure 🔍 -2% - +1% -16.20ms - +13.74ms	-

split-button permalink

Version	Bytes	Avg Time	vs remote	vs branch
npm latest	710 kB	1902.65ms - 1906.82ms	-	unsure 🔍 -0% - +0% -4.51ms - +1.62ms
branch	696 kB	1903.93ms - 1908.43ms	unsure 🔍 -0% - +0% -1.62ms - +4.51ms	-

Firefox

action-menu permalink

Version	Bytes	Avg Time	vs remote	vs branch
npm latest	639 kB	545.13ms - 579.59ms	-	unsure 🔍 -4% - +4% -23.91ms - +21.23ms
branch	625 kB	549.12ms - 578.28ms	unsure 🔍 -4% - +4% -21.23ms - +23.91ms	-

menu permalink

Version	Bytes	Avg Time	vs remote	vs branch
npm latest	461 kB	763.24ms - 814.04ms	-	unsure 🔍 -7% - +3% -59.41ms - +20.93ms
branch	448 kB	776.76ms - 839.00ms	unsure 🔍 -3% - +8% -20.93ms - +59.41ms	-

picker permalink

Version	Bytes	Avg Time	vs remote	vs branch
npm latest	505 kB	1424.61ms - 1482.39ms	-	unsure 🔍 -3% - +3% -39.11ms - +36.43ms
branch	491 kB	1430.52ms - 1479.16ms	unsure 🔍 -3% - +3% -36.43ms - +39.11ms	-

split-button permalink

Version	Bytes	Avg Time	vs remote	vs branch
npm latest	710 kB	1640.14ms - 1660.78ms	-	unsure 🔍 -1% - +1% -13.38ms - +15.90ms
branch	696 kB	1638.82ms - 1659.58ms	unsure 🔍 -1% - +1% -15.90ms - +13.38ms	-

[Westbrook]

Thanks!