fix: QDatetimeRange vertical alignment if one field is empty and one is not

[pdanpdan]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
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Does this PR introduce a breaking change? (check one)

• Yes
• No

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• It's submitted to the dev branch and not the master branch
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix: #xxx[,#xxx], where "xxx" is the issue number)
• It's been tested with all Quasar themes
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If adding a new feature, the PR's description includes:

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Other information:

In case one of the fields in QDatetimeRange has value and one has not the fields are missaligned.
This fix uses the same styles as the .full-width version, but widthout flex-grow 1

[rstoenescu]

Hi, the fix is good. But can you please redo the PR on a different branch? Seems like more commits have gone into this PR than the initial one. Thank you very much for taking time to investigate and fix!