I would like to pay your attention to the ParametrizedAction throws the NullReferenceException when TabbedMDI is used issue, which you may encounter in the version 14.2.6.
Turning off the tabbed MDI mode can temporarily help you avoid this error, but this is not very suitable. So, I strongly recommend you download a patch from here.
Please accept sincerely apologies from our team for all the inconvenience here.