AccessViolationException when using RibbonDropDownColorPicker in 64-bit

[ThomasHaberl]

Assigning an array of strings to the RibbonDropDownColorPicker.ThemeColorsTooltips property will cause an AccessViolationException when the application is executed as a 64-bit process. The exception occurs in line 640 of ColorPickerPropertiesProvider.cs, the call to UIRibbonFramework.SetUICommandProperty() in said property.

It can be reproduced with the following sample project:
RibbonLib.Sample.zip

This project is based on sample "11 - DropDownColorPicker" of the original Windows Ribbon for WinForms (https://windowsribbon.codeplex.com/). The only relevant change was that I disabled the "Prefer 32-bit" option in the project's properties. The original implementation has the same problem. It seems like array pointers in the PropVariant structure are marshalled incorrectly in 64-bit scenarios.