add blank material files

gearbox/pbr/models/pit_drone.mdl/pit_drone.mdl.mat

@@ -0,0 +1,8 @@
+
+{
+"for" "#models/pit_drone/pit_drone_01.mdl"
+//"basecolor_map" "pit_drone_01.png"
+//"normal_map" "pit_drone_01_normal.png"
+//"metal_map" "pit_drone_01_metal.png"
+//"roughness_map" "pit_drone_01_roughness.png"
+}