Troubleshooting "Object Reference Not Set to an Instance of an Object" Error in AD FS

Question

I'm encountering an issue while editing claim rules in Active Directory Federation Services (AD FS). When I try to modify claim rules under Claims Provider Trusts, I get the following error message:

Unhandled exception has occurred in your application. Object reference not set to an instance of an object.

The error appears in a pop-up window, and the details mention an issue with System.Windows.Forms.ComboBox.
There is no error message on Event Viewer.
Please help me review image below and suggest for me the solution or root cause for this issue.

Thanks,
Tri