// Prompt user to perform color adjustment effects when an Image Layer is selected works beautifully:
var Executed := ImageEnView1.Proc.DoPreviews( ppeColorAdjustments );
// Prompt user to perform color adjustment effects when a Shape Layer is selected CRASHES the App in some cases:
var Executed := ImageEnView1.Proc.DoPreviews( ppeColorAdjustments );
Here is the stack:

Since the user doesn't want to get a university diploma about which layer types he can edit with which preview dialog, a feature should automatically prevent such incompatibilities by not opening ppeColorAdjustments with a Shape layer. That would be very user-friendly!