Steps to reproduce:

1. Create new Unity project
2. Create new script and add two public Gradients. For example:
public Gradient firstGradient;
public Gradient secondGradient;
3. Attach the script to any game object
4. Select the game object, right-click one of the gradients in the inspector and click 'Copy'
5. Right-click another gradient, click 'Paste'
6. The value does not get pasted and few seconds after, the editor crashes