Regression of the table/panel clipping

Created by: supergibbs

Not in v3.2 but in the latest from GitHub, the corners are getting clipped by the background of the table row.

It's caused by these two commits from #13920: ac67bc85 71974e2f

Any table-striping (or manual background colors) need to go on the td/th, not the tr if it's in a panel.