When selecting multiple objects of different types in the Project window, the Inspector no longer displays a list of Objects, per type.

repro:
-in the Project window, create a new folder and a new material
-select both Objects and look at the Inspector

bug: only "New Folder" object is inspected
... and error is thrown in the console...
NullReferenceException: Object reference not set to an instance of an object
UnityEditor.Editor.DrawHeaderGUI (UnityEditor.Editor editor, System.String header, Single leftMargin) (at /Users/builduser/buildslave/unity/build/Editor/Mono/Inspector/Editor.cs:486)
UnityEditor.Editor.DrawHeaderGUI (UnityEditor.Editor editor, System.String header) (at /Users/builduser/buildslave/unity/build/Editor/Mono/Inspector/Editor.cs:465)
UnityEditor.InspectorWindow.DrawSelectionPickerList () (at /Users/builduser/buildslave/unity/build/Editor/Mono/Inspector/InspectorWindow.cs:1328)
UnityEditor.InspectorWindow.OnGUI () (at /Users/builduser/buildslave/unity/build/Editor/Mono/Inspector/InspectorWindow.cs:366)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)

expected: 2 Objects listed (see attached image)

found in...
Version 2017.1.0b1 (24768443e8a3)
Branch: trunk

regression from... Version 5.6.0f3 (497a0f351392)