Hello,
It seems that there is a bug in the RibbonTool class. NullReferenceException is raised when setting the Command property to null. Can you please fix it in the upcoming service release?
Thanks,
Gary
HI,
I was not able to reproduce your issue using the 12.1 release build.
I am attaching my sample, please feel free to modify it so that it replicates your issue.
Sincerely,
Matt, Developer Support Engineer