Error when attempting to optimize.

[thehollowedone]

ArgumentNullException: Value cannot be null.
Parameter name: key
System.Collections.Generic.Dictionary`2[TKey,TValue].TryInsert (TKey key, TValue value, System.Collections.Generic.InsertionBehavior behavior) (at <eae584ce26bc40229c1b1aa476bfa589>:0)
System.Collections.Generic.Dictionary`2[TKey,TValue].Add (TKey key, TValue value) (at <eae584ce26bc40229c1b1aa476bfa589>:0)
System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement] (System.Collections.Generic.IEnumerable`1[T] source, System.Func`2[T,TResult] keySelector, System.Func`2[T,TResult] elementSelector, System.Collections.Generic.IEqualityComparer`1[T] comparer) (at <351e49e2a5bf4fd6beabb458ce2255f3>:0)
System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement] (System.Collections.Generic.IEnumerable`1[T] source, System.Func`2[T,TResult] keySelector, System.Func`2[T,TResult] elementSelector) (at <351e49e2a5bf4fd6beabb458ce2255f3>:0)
d4rkAvatarOptimizer.OptimizeMaterialsOnNonSkinnedMeshes () (at Packages/d4rkpl4y3r.d4rkavataroptimizer/Editor/d4rkAvatarOptimizer.cs:3146)
d4rkAvatarOptimizer.Optimize () (at Packages/d4rkpl4y3r.d4rkavataroptimizer/Editor/d4rkAvatarOptimizer.cs:158)
d4rkAvatarOptimizerEditor.OnInspectorGUI () (at Packages/d4rkpl4y3r.d4rkavataroptimizer/Editor/d4rkAvatarOptimizerEditor.cs:137)
UnityEditor.UIElements.InspectorElement+<>c__DisplayClass58_0.<CreateIMGUIInspectorFromEditor>b__0 () (at <a259d3c004024353a2c217da97495055>:0)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

All shaders locked, not sure what causes it.

[d4rkc0d3r]

I could reproduce this crash. One of your non skinned meshes has a missing material.