Catmull-Clark Error, "Array is empty"

Hi everyone,

I am fairly inexperienced with grasshopper and its various plugins so I am having a tough time trying to work this issue out on my own. I have been following an online tutorial: https://www.youtube.com/watch?v=DP975CpmuTA on how to make a diamond grid building skin. However, when I reach this last step, I receive an error when plugging my mesh into a catmull-clark subdivision saying "Array is empty". I am thinking it may have something with the invalid mesh entries shown in the list, however I am not really sure how to remove them.

Thanks for your help!