add missing default

src/material/lightmappedgeneric.rs

@@ -71,7 +71,7 @@ pub struct LightMappedGenericMaterial {
     pub translucent: bool,
 
     /// Specifies a texture that will provide three-dimensional lighting information for a material.
-    #[serde(rename = "$bumpmap", deserialize_with = "deserialize_path")]
+    #[serde(rename = "$bumpmap", default, deserialize_with = "deserialize_path")]
     pub bump_map: Option<String>,
     /// Per-texel color modification via a warp texture.
     #[serde(

src/material/worldvertextransition.rs

@@ -15,6 +15,7 @@ pub struct WorldVertexTransitionMaterial {
     /// Modulate the blending between materials using a special texture.
     #[serde(
         rename = "$blendmodulatetexture",
+        default,
         deserialize_with = "deserialize_path"
     )]
     pub blend_modulate_texture: Option<String>,