To reproduce:

1. Create a new project
2. Import System.Data.Entity.dll from C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\v3.5
3. Select the imported dll file
4. Observe the console

Expected: importing a .dll into the project does throw any errors and user is able to change .dll import settings
Actual: IndexOutOfRangeException and warning "Unexpected top level layout group!..." are shown in the console when the imported dll is selected

Reproduced in 5.4.5p1, 5.4.5p2
Did not reproduce in 5.3.8f1, 5.4.0f3, 5.4.5f1, 5.5.1f1, 5.6.1p1, 2017.1.0b5
Regression introduced in 5.4.5p1