Issue with Landscape Layer Blending Node compile in UE 5.4.2

When the SetMaterialAttributes Material Expression is used without an input to MaterialAttributes, it will cause Landscape Layer Blend expressions to fail to compile if it is the only layer on a particular component.

Also tested in UE5-Main, CL: 35136630. The behavior was slightly different. Instead of failing to compile the shaders, the landscape components that are entirely covered in the layer using SetMaterialAttributes are offset downwards by about 210 units.

1. Download the attached test project and open.
2. Observe that the landscape has two layers: a red layer (A) and a blue layer (B).
3. Observe that some of the landscape components are entirely composed of the red layer (A).
4. Open the Material Instance "/Game/MI_LandscapeAuto"
5. Observe that there are two Global Static Switch Parameters:
"Layer1: T:Make F:Set or SetFix"
"Layer1: T:SetFix F:Set"
6. Test the permutations of enabled / disabled for each.
7. Observe that when both are disabled, there are shader compiler errors reported in the log, and that the landscape components that are entirely composed of the red layer (A) are using a fallback material to render.