I have added a Add-in Module project in Visualt Studio with default settings and added a ArcGIS Pro Dockpane with BurgerButton control with default settings - no changes at all. When running the project I get a NullReferenceException before hitting any breakpoints in the code and before ArcGIS Pro has launched. I see the ArcGIS Pro splash screen and then I get the exception in Visual Studio. Adding an ArcGIS Pro Button works.
The error message is: "An unhandled exception of type 'System.NullReferenceException' occurred in mscorlib.dll"
I am using Visual Studio 2015 Update 3 and ArcGIS Pro SDK 184.108.40.20698.