Small fix for null names on materials

Author: Kinerius

Runtime/GLTFastWrappers/DecentralandMaterialGenerator.cs

@@ -82,10 +82,10 @@ private void SetMaterialName(int materialIndex, GLTFastMaterial gltfMaterial)
         {
             material.name = "material";
 
-            string originalName = gltfMaterial.name.ToLower();
-
-            if (!string.IsNullOrEmpty(originalName))
+            if (!string.IsNullOrEmpty(gltfMaterial.name))
             {
+                string originalName = gltfMaterial.name.ToLower();
+
                 if (originalName.Contains("skin"))
                     material.name += "_skin";