[Stack] Ensure that marginundefined doesn't occur in styling

[hbjORbj]

• I have followed (at least) the PR section of the contributing guide.

Closes #32196

Problem:

• If direction prop receives a responsive value such that it doesn't start with the smallest breakpoint, such as direction={{ lg: 'row' }}, for the breakpoints below lg, "marginundefined": "0px"is being used in styling instead of "marginLeft": "0px" (for row direction) or "marginTop": "0px" (for column direction).
• This function in line 86 results in undefined because directionValues[breakpoint] in the next line, line 87, is undefined.

Solution:

• Ensure that this function in line 86 never results in undefined, by ensuring that directionValues[breakpoint] in the next line, line 87, is not undefined.

Codesandboxes:

• Before

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• After

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[mui-bot]

Details of bundle changes

Generated by 🚫 dangerJS against 73cc0a6

[mnajdova]

LGTM