Sidebar hover disabled due to crash when reading highlightedSidebarLayers

[ellbosch]

Repro steps:

1. Remove the commented out code flagged by // TODO: reads here cause a crash nodes once connected to layer inputs nodes
2. Create a patch node and any layer node (i.e. Oval layer node)
3. Create a node for one of the layer node's inputs (i.e. the position input)
4. Connect the patch node's output to the layer input node
5. Open the left-hand sidebar and hover over an element

You'll notice an unsafe memory access crash when this happens.

Unclear why this happens with this exact criteria—the state gets set inside a SwiftUI .onHover. It appears that all reads and writes take place on the main thread.