To reproduce:
1. Undock scene view
2. Duoble click scene view tab and start draging scene view window after first click

Actual: Editor crashes

Reproducible: 2017.01b5, 2017.01a4
Not reproducible: 2017.01a3

Not reproducible on macOS.

Stack trace:

0x000000014032623F (Unity) std::_Tree<std::_Tmap_traits<core::basic_string<char,core::StringStorageDefault<char> >,int,std::less<core::basic_string<char,core::StringStorageDefault<char> > >,std::allocator<std::pair<core::basic_string<char,core::StringStorageDefault<char> > const ,int> >,1> >::_Erase
0x000000014032A661 (Unity) std::_Tree<std::_Tmap_traits<core::basic_string<char,core::StringStorageDefault<char> >,int,std::less<core::basic_string<char,core::StringStorageDefault<char> > >,std::allocator<std::pair<core::basic_string<char,core::StringStorageDefault<char> > const ,int> >,1> >::erase
0x000000014102E785 (Unity) GUIKeyboardState::~GUIKeyboardState
0x000000014002D53F (Unity) GUIView::~GUIView
0x000000014002E504 (Unity) GUIView::`vector deleting destructor'
0x000000014175AD9E (Unity) GUIView_CUSTOM_Internal_Close
0x000000003314A5FD (Mono JIT Code) (wrapper managed-to-native) UnityEditor.GUIView:Internal_Close ()
0x000000003314A447 (Mono JIT Code) [C:\buildslave\unity\build\Editor\Mono\GUIView.cs:207] UnityEditor.GUIView:OnDestroy ()
0x0000000033149E18 (Mono JIT Code) [C:\buildslave\unity\build\Editor\Mono\HostView.cs:129] UnityEditor.HostView:OnDestroy ()
0x000000003316FA68 (Mono JIT Code) [C:\buildslave\unity\build\Editor\Mono\GUI\DockArea.cs:95] UnityEditor.DockArea:OnDestroy ()
0x00000000008B6C42 (Mono JIT Code) (wrapper runtime-invoke) object:runtime_invoke_void__this__ (object,intptr,intptr,intptr)
0x00007FF9FCF85A97 (mono) [c:\buildslave\mono\build\mono\mini\mini.c:4937] mono_jit_runtime_invoke
0x00007FF9FCED8741 (mono) [c:\buildslave\mono\build\mono\metadata\object.c:2623] mono_runtime_invoke
0x00000001413E87C5 (Unity) scripting_method_invoke
0x00000001413E0991 (Unity) ScriptingInvocation::Invoke
0x00000001413E2CDE (Unity) ScriptingInvocation::InvokeChecked
0x000000014114AD04 (Unity) MonoBehaviour::CallMethodInactive
0x000000014114BD58 (Unity) MonoBehaviour::WillDestroyComponent
0x00000001410A07A2 (Unity) DestroyObjectHighLevel
0x00000001413CE1F0 (Unity) Scripting::DestroyObjectFromScriptingImmediate
0x00000000331490CD (Mono JIT Code) (wrapper managed-to-native) UnityEngine.Object:DestroyImmediate (UnityEngine.Object,bool)
0x000000003316671E (Mono JIT Code) [C:\buildslave\unity\build\Editor\Mono\GUI\DockArea.cs:231] UnityEditor.DockArea:KillIfEmpty ()
0x00000000331640BA (Mono JIT Code) [C:\buildslave\unity\build\Editor\Mono\GUI\DockArea.cs:210] UnityEditor.DockArea:RemoveTab (UnityEditor.EditorWindow,bool)
0x0000000033180EA1 (Mono JIT Code) [C:\buildslave\unity\build\Editor\Mono\GUI\DockArea.cs:271] UnityEditor.DockArea:PerformDrop (UnityEditor.EditorWindow,UnityEditor.DropInfo,UnityEngine.Vector2)
0x0000000014DEB122 (Mono JIT Code) [C:\buildslave\unity\build\Editor\Mono\GUI\DockArea.cs:699] UnityEditor.DockArea:DragTab (UnityEngine.Rect,UnityEngine.GUIStyle)
0x0000000014DD01A4 (Mono JIT Code) [C:\buildslave\unity\build\Editor\Mono\GUI\DockArea.cs:398] UnityEditor.DockArea:OldOnGUI ()
0x0000000014DB543F (Mono JIT Code) [C:\buildslave\unity\build\Runtime\UIElements\Managed\IMGUIContainer.cs:104] UnityEngine.Experimental.UIElements.IMGUIContainer:DoOnGUI (UnityEngine.Event)
0x0000000014DB48EA (Mono JIT Code) [C:\buildslave\unity\build\Runtime\UIElements\Managed\IMGUIContainer.cs:159] UnityEngine.Experimental.UIElements.IMGUIContainer:HandleEvent (UnityEngine.Event,UnityEngine.Experimental.UIElements.VisualElement)
0x0000000014DB2548 (Mono JIT Code) [C:\buildslave\unity\build\Runtime\UIElements\Managed\EventDispatcher.cs:232] UnityEngine.Experimental.UIElements.EventDispatcher:DispatchEvent (UnityEngine.Event,UnityEngine.Experimental.UIElements.IVisualElementPanel)
0x0000000014D9C7D2 (Mono JIT Code) [C:\buildslave\unity\build\Runtime\UIElements\Managed\UIElementsUtility.cs:214] UnityEngine.Experimental.UIElements.UIElementsUtility:DoDispatch (UnityEngine.Experimental.UIElements.IVisualElementPanel)
0x0000000014D9C36B (Mono JIT Code) [C:\buildslave\unity\build\Runtime\UIElements\Managed\UIElementsUtility.cs:67] UnityEngine.Experimental.UIElements.UIElementsUtility:ProcessEvent (int,intptr)
0x0000000014D9BE8D (Mono JIT Code) [C:\buildslave\unity\build\Runtime\IMGUI\Managed\GUIUtility.cs:186] UnityEngine.GUIUtility:ProcessEvent (int,intptr)
0x0000000014D9C04E (Mono JIT Code) (wrapper runtime-invoke) <Module>:runtime_invoke_bool_int_intptr (object,intptr,intptr,intptr)
0x00007FF9FCF85A97 (mono) [c:\buildslave\mono\build\mono\mini\mini.c:4937] mono_jit_runtime_invoke
0x00007FF9FCED8741 (mono) [c:\buildslave\mono\build\mono\metadata\object.c:2623] mono_runtime_invoke
0x00000001413E87C5 (Unity) scripting_method_invoke
0x00000001413E0991 (Unity) ScriptingInvocation::Invoke
0x00000001401BCA0B (Unity) GUIView::ProcessRetainedMode
0x000000014002971F (Unity) GUIView::OnInputEvent
0x00000001401AFC13 (Unity) GUIView::ProcessInputEvent
0x0000000140006AC3 (Unity) GUIView::ProcessEventMessages
0x000000014002D285 (Unity) GUIView::GUIViewWndProc
0x00007FFA2B941C24 (USER32) CallWindowProcW
0x00007FFA2B94156C (USER32) DispatchMessageW
0x0000000141A60ABA (Unity) MainMessageLoop
0x0000000141A624E7 (Unity) WinMain
0x0000000141CC428C (Unity) __tmainCRTStartup
0x00007FFA29268364 (KERNEL32) BaseThreadInitThunk
0x00007FFA2BD370D1 (ntdll) RtlUserThreadStart