Changing the channel name inside of the channel mask parameter node results in crash

Changing the name of a channel inside of the channel mask parameter node results in a crash.

1. Create a new material
2. Inside of the material, add a channel mask parameter node 
3. Change any of the channel names then press enter

Result: Crash

Expected: Successful channel name change

Assertion failed: (Index >= 0) & (Index < ArrayNum) [Link Removed] [Line: 614] Array index out of bounds: 1 from an array of size 1

UE4Editor_Core!AssertFailedImplV() [d:\build\++ue4\sync\engine\source\runtime\core\private\misc\assertionmacros.cpp:105]
UE4Editor_Core!FDebug::CheckVerifyFailedImpl() [d:\build\++ue4\sync\engine\source\runtime\core\private\misc\assertionmacros.cpp:455]
UE4Editor_Engine!DispatchCheckVerify<void,<lambda_0b9040f9199928a3836d925baab88b90> >() [d:\build\++ue4\sync\engine\source\runtime\core\public\misc\assertionmacros.h:168]
UE4Editor_Engine!UMaterialExpressionVectorParameter::ApplyChannelNames() [d:\build\++ue4\sync\engine\source\runtime\engine\private\materials\materialexpressions.cpp:7297]
UE4Editor_Engine!UMaterialExpressionChannelMaskParameter::PostEditChangeProperty() [d:\build\++ue4\sync\engine\source\runtime\engine\private\materials\materialexpressions.cpp:7471]
UE4Editor_CoreUObject!UObject::PostEditChangeChainProperty() [d:\build\++ue4\sync\engine\source\runtime\coreuobject\private\uobject\obj.cpp:449]
UE4Editor_PropertyEditor!FPropertyNode::NotifyPostChange() [d:\build\++ue4\sync\engine\source\editor\propertyeditor\private\propertynode.cpp:2183]
UE4Editor_PropertyEditor!FPropertyValueImpl::ImportText() [d:\build\++ue4\sync\engine\source\editor\propertyeditor\private\propertyhandleimpl.cpp:621]
UE4Editor_PropertyEditor!<lambda_e0880ca4ad6ea22afc616f1e692f6605>::operator()() [d:\build\++ue4\sync\engine\source\editor\propertyeditor\private\propertyhandleimpl.cpp:2808]
UE4Editor_PropertyEditor!FPropertyValueImpl::EnumerateObjectsToModify() [d:\build\++ue4\sync\engine\source\editor\propertyeditor\private\propertyhandleimpl.cpp:121]
UE4Editor_PropertyEditor!FPropertyHandleBase::SetPerObjectValue() [d:\build\++ue4\sync\engine\source\editor\propertyeditor\private\propertyhandleimpl.cpp:2796]
UE4Editor_DetailCustomizations!`anonymous namespace'::FEditableTextPropertyHandle::SetText() [d:\build\++ue4\sync\engine\source\editor\detailcustomizations\private\textcustomization.cpp:81]
UE4Editor_EditorWidgets!STextPropertyEditableTextBox::OnTextCommitted() [d:\build\++ue4\sync\engine\source\editor\editorwidgets\private\stextpropertyeditabletextbox.cpp:1122]
UE4Editor_EditorWidgets!TBaseSPMethodDelegateInstance<0,STextPropertyEditableTextBox,0,void __cdecl(FText const &,enum ETextCommit::Type)>::ExecuteIfSafe() [d:\build\++ue4\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:369]
UE4Editor_Slate!SEditableText::OnTextCommitted() [d:\build\++ue4\sync\engine\source\runtime\slate\private\widgets\input\seditabletext.cpp:598]
UE4Editor_Slate!FSlateEditableTextLayout::HandleCarriageReturn() [d:\build\++ue4\sync\engine\source\runtime\slate\private\widgets\text\slateeditabletextlayout.cpp:1514]
UE4Editor_Slate!FSlateEditableTextLayout::HandleKeyDown() [d:\build\++ue4\sync\engine\source\runtime\slate\private\widgets\text\slateeditabletextlayout.cpp:967]
UE4Editor_Slate!SEditableText::OnKeyDown() [d:\build\++ue4\sync\engine\source\runtime\slate\private\widgets\input\seditabletext.cpp:211]
UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FBubblePolicy,FKeyEvent,<lambda_884ae9969c3cb3acb5f6265b67adef4c> >() [d:\build\++ue4\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:372]
UE4Editor_Slate!FSlateApplication::ProcessKeyDownEvent() [d:\build\++ue4\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:4151]
UE4Editor_Slate!FSlateApplication::OnKeyDown() [d:\build\++ue4\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:4059]
UE4Editor_ApplicationCore!FWindowsApplication::ProcessDeferredMessage() [d:\build\++ue4\sync\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:1793]
UE4Editor_ApplicationCore!FWindowsApplication::DeferMessage() [d:\build\++ue4\sync\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:2410]
UE4Editor_ApplicationCore!FWindowsApplication::ProcessMessage() [d:\build\++ue4\sync\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:1638]
UE4Editor_ApplicationCore!FWindowsApplication::AppWndProc() [d:\build\++ue4\sync\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:789]
user32
user32
UE4Editor_ApplicationCore!FWindowsPlatformApplicationMisc::PumpMessages() [d:\build\++ue4\sync\engine\source\runtime\applicationcore\private\windows\windowsplatformapplicationmisc.cpp:130]
UE4Editor!FEngineLoop::Tick() [d:\build\++ue4\sync\engine\source\runtime\launch\private\launchengineloop.cpp:4397]
UE4Editor!GuardedMain() [d:\build\++ue4\sync\engine\source\runtime\launch\private\launch.cpp:173]
UE4Editor!GuardedMainWrapper() [d:\build\++ue4\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:134]
UE4Editor!WinMain() [d:\build\++ue4\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:263]
UE4Editor!__scrt_common_main_seh() [d:\agent\_work\2\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
kernel32
ntdll