Parts of explorer panel has different border radiuses, leading to white corners

[tephenavies]

Apply these fixes:

<div class="tjs-tabs__panel-content tjs-_base__clearfix" style="border-radius: 0 0 3px 3px;">

<div id="explorer-panel" class="tjs-explorer-window__explorer-panel tjs-explorer-window__is-mounted" aria-labelledby="modalTitle" aria-describedby="modalDescription" role="dialog" style="background: unset;">

Actually, the shadow from the explorer panel comes from a smaller div than the content of the explorer panel. Better fix this too. This is because panels in the div have a height of 70vh, but the containing div has a different size set. And it's this containing div (second in the above HTML snippets) that has the shadow.

[zoran995]

This should be resolved in https://github.com/TerriaJS/terriajs/pull/6466