[WC-3280] DG: Fix unwanted scrollbar for cleared grids

[yordan-st]

Pull request type

Bug fix (non-breaking change which fixes an issue)

---

Description

• Clearing a grid to 0 rows, would cause a unwanted recalculation of column widths, causing columns to overflow and in turn add scrollbars. This fix is aimed at making sure that: for empty grids the grid columns use the natural css grid layout instead of recalculating the column widths.

What should be covered while testing?

• Add a tooltip with a small image in the header filter
• Set the width of that column to auto-fit content and for min-width property try both auto and set by content
• Observe if the column width change weirdly when adding / deleting a row.
• Observe the same if you add / delete and then leave and return to the page.