title: Unity C# - Cannot perform upm operation: Cannot read property 'map' of undefined [NotFound]
body: <p>I am developing a game 3D under UNITY ( Unity 2020.1.3f1 ) with C# on windows, all things everything was working fine, suddenly the following error appears :</p>
  <p><em><strong>Cannot perform upm operation: Cannot read property 'map' of undefined [NotFound].See console for more details
  UnityEditor.EditorApplication:Internal_CallUpdateFunctions()</strong></em></p>
  <p><a href="https://i.stack.imgur.com/vWqpa.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/vWqpa.png" alt="enter image description here" /></a></p>
  <p>And on the Package Manager in the Unity Registry i can't refreshing packages :</p>
  <p><a href="https://i.stack.imgur.com/7bnYa.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7bnYa.png" alt="enter image description here" /></a></p>
  <p>And the game on android crash on startup but it works on editor without any error</p>
  <p>I found no explanation for this error and all the topics that talk about this error he talks about reactjs while I code with C# no relation with reactjs</p>
  <p>Please Help me</p>