Mansion foundations are interrupted by vegetation

Partially fixed so that the trees don't generate under the mansion now. They still will interrupt the foundation, but only if the trees end up too close to the mansion. I also updated the screenshots accordingly.

Can confirm in 21w16a.

Now it affects the trees next to the entrance, but somehow the ones in the given location don't interrupt the foundation anymore.

Edit: can this issue be renamed into "Mansion foundations are interrupted by vegetation", so that it can also include grass and other non-solid plants? (see image above)