Apply Dialog Failed upon Applying Conditions to Topic

[ValerieFarber]

I recently added a set of conditions to a large project. When I try to apply a condition to a topic I get the following error: "Apply Dialog failed. Object reference not set to an instance of an object." What is causing this? How do I fix it? The large project has GIT source control. I made a mini project without source control for learning how to work with conditions and copied several pages from the large project. In the mini-project I can apply conditions to topics.
Please help solve. Thank you
Valerie Farber