Fix WMS null rectangle check + inherit bbox from ancestor WMS Layers

[nf-s]

Fix WMS null rectangle check + inherit bbox from ancestor WMS Layers

Fixes #6860

There was a bug that was causing WebMapServiceCatalogItem.rectangle to be {"west": 0,"south": 0,"east": 0,"north": 0} which was breaking cesium internals. I fixed this with a null check.

Additionally, in the WMS spec (for both 1.3.0 and 1.1.1), you can have a hierarchy of Layers and certain parent properties can be inherited by child Layers - for example EX_GeographicBoundingBox - which is used to calculate rectangle. So I added ability to work up through Layer ancestors until a EX_GeographicBoundingBox is found.

In the test case below, the child Layer of interest doesn't have a EX_GeographicBoundingBox, but it's parent does - so it should inherit it.

Changes

• Add null check to WebMapServiceCatalogItem rectangle calculation - and now we ascend tree of WMS Layers until we find a rectangle.

Test me

• On main test link
• After fix test link

Checklist

• There are unit tests to verify my changes are correct or unit tests aren't applicable (if so, write quick reason why unit tests don't exist)
• I've updated relevant documentation in doc/.
• I've updated CHANGES.md with what I changed.
• I've provided instructions in the PR description on how to test this PR.

[na9da]

@nf-s - the changes look good to me.

Just left a small comment.
Also, please remember to move change under the new version header in CHANGES.md.