Remove palettes from base IRenderable.

OpenRA.Mods.Common/Traits/Render/WithShadow.cs

@@ -49,8 +49,8 @@ namespace OpenRA.Mods.Common.Traits.Render
 
 			// Contrails shouldn't cast shadows
 			var height = self.World.Map.DistanceAboveTerrain(self.CenterPosition).Length;
-			var shadowSprites = r.Where(s => !s.IsDecoration)
-				.Select(a => a.WithPalette(wr.Palette(info.Palette))
+			var shadowSprites = r.Where(s => !s.IsDecoration && s is IPalettedRenderable)
+				.Select(a => ((IPalettedRenderable)a).WithPalette(wr.Palette(info.Palette))
 					.OffsetBy(info.Offset - new WVec(0, 0, height))
 					.WithZOffset(a.ZOffset + (height + info.ZOffset))
 					.AsDecoration());