Fix(web-twig): Do not render CSS property in the GridItem style attribute if the value is empty

[dlouhak]

I was going around… Small nitpicking. ✨ ⛏️

When we needed to send a null value to a prop, the CSS property was generated without an assigned value.

Source code from Jobs.cz

<GridItem
      columnStart="{{ gridItemColumnStart ? gridItemColumnStart[loop.index] : null }}"
      columnEnd="{{ gridItemColumnEnd ? gridItemColumnEnd[loop.index] : null }}"
      rowStart="{{ gridItemRowStart ? gridItemRowStart[loop.index] : null }}"
      rowEnd="{{ gridItemRowEnd ? gridItemRowEnd[loop.index] : null }}"
  >
      <MedallionGalleryImage image="{{ image }}" />
  </GridItem>

→

😞 Current output

<div
    class="GridItem"
    style="--grid-item-column-start: ;--grid-item-column-end: ;--grid-item-row-start: ;--grid-item-row-end: ;"
>...</div>

✨ Upcoming output

<div class="GridItem">...</div>

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[coveralls]

coverage: 96.491%. remained the same
when pulling fcf2b59 on feature/griditem-do-not-render-style-attribute-with-empty-value
into b1d558b on main.

[literat]

LGTM 👍 Thanks a lot :-)