Syncing a texture from source control while a material editor sampling it is open will crash the editor

Syncing to source control will cause a crash if a texture is synced that is being referenced by an open material editor, even if the texture hasn't been modified. A quick solution may be to close the material editor when a sync occurs, but it may be possible for the material editor to better handle the hot reload.

1. Create a texture and a material, and check them in to source control
2. Edit your material to sample your texture
3. With the material still open, right click you content folder and Sync
4. Editor will crash upon trying to hot reload the texture being referenced by the material editor

UE4Editor_CoreUObject!PackageReloadInternal::LoadReplacementPackage() [d:\ue4deveditor\engine\source\runtime\coreuobject\private\uobject\packagereload.cpp:261]
UE4Editor_CoreUObject!ReloadPackages() [d:\ue4deveditor\engine\source\runtime\coreuobject\private\uobject\packagereload.cpp:451]
UE4Editor_UnrealEd!PackageTools::ReloadPackages() [d:\ue4deveditor\engine\source\editor\unrealed\private\packagetools.cpp:608]
UE4Editor_UnrealEd!PackageTools::ReloadPackages() [d:\ue4deveditor\engine\source\editor\unrealed\private\packagetools.cpp:425]
UE4Editor_ContentBrowser!ContentBrowserUtils::SyncPathsFromSourceControl() [d:\ue4deveditor\engine\source\editor\contentbrowser\private\contentbrowserutils.cpp:2152]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<1,FPathContextMenu,0,TTypeWrapper<void> __cdecl(void)>::Execute() [d:\ue4deveditor\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:269]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<1,FPathContextMenu,0,void __cdecl(void)>::ExecuteIfSafe() [d:\ue4deveditor\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:345]
UE4Editor_Slate!SMenuEntryBlock::OnClicked() [d:\ue4deveditor\engine\source\runtime\slate\private\framework\multibox\smenuentryblock.cpp:1037]
UE4Editor_Slate!SMenuEntryBlock::OnMenuItemButtonClicked() [d:\ue4deveditor\engine\source\runtime\slate\private\framework\multibox\smenuentryblock.cpp:988]
UE4Editor_Slate!TMemberFunctionCaller<SMenuEntryBlock,FReply (__cdecl SMenuEntryBlock::*)(void) __ptr64>::operator()<>() [d:\ue4deveditor\engine\source\runtime\core\public\delegates\delegateinstanceinterface.h:156]
UE4Editor_Slate!UE4Tuple_Private::TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter<TMemberFunctionCaller<SMenuEntryBlock,FReply (__cdecl SMenuEntryBlock::*)(void) __ptr64> >() [d:\ue4deveditor\engine\source\runtime\core\public\templates\tuple.h:504]
UE4Editor_Slate!TBaseSPMethodDelegateInstance<0,SMenuEntryBlock,0,FReply __cdecl(void)>::Execute() [d:\ue4deveditor\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:269]
UE4Editor_Slate!TBaseDelegate<FReply>::Execute() [d:\ue4deveditor\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:537]
UE4Editor_Slate!SButton::OnMouseButtonUp() [d:\ue4deveditor\engine\source\runtime\slate\private\widgets\input\sbutton.cpp:282]
UE4Editor_Slate!SMenuEntryButton::OnMouseButtonUp() [d:\ue4deveditor\engine\source\runtime\slate\private\framework\multibox\smenuentryblock.cpp:385]
UE4Editor_Slate!<lambda_1002768c627006711ef2f351a87ec0e7>::operator()() [d:\ue4deveditor\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5442]
UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_1002768c627006711ef2f351a87ec0e7> >() [d:\ue4deveditor\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:268]
UE4Editor_Slate!FSlateApplication::RoutePointerUpEvent() [d:\ue4deveditor\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5431]
UE4Editor_Slate!FSlateApplication::ProcessMouseButtonUpEvent() [d:\ue4deveditor\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5929]
UE4Editor_Slate!FSlateApplication::OnMouseUp() [d:\ue4deveditor\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5909]
UE4Editor_ApplicationCore!FWindowsApplication::ProcessDeferredMessage() [d:\ue4deveditor\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:1726]
UE4Editor_ApplicationCore!FWindowsApplication::DeferMessage() [d:\ue4deveditor\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:2172]
UE4Editor_ApplicationCore!FWindowsApplication::ProcessMessage() [d:\ue4deveditor\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:889]
UE4Editor_ApplicationCore!FWindowsApplication::AppWndProc() [d:\ue4deveditor\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:726]
user32
user32
UE4Editor_ApplicationCore!FWindowsPlatformApplicationMisc::PumpMessages() [d:\ue4deveditor\engine\source\runtime\applicationcore\private\windows\windowsplatformapplicationmisc.cpp:129]
UE4Editor!FEngineLoop::Tick() [d:\ue4deveditor\engine\source\runtime\launch\private\launchengineloop.cpp:3302]
UE4Editor!GuardedMain() [d:\ue4deveditor\engine\source\runtime\launch\private\launch.cpp:166]
UE4Editor!GuardedMainWrapper() [d:\ue4deveditor\engine\source\runtime\launch\private\windows\launchwindows.cpp:134]
UE4Editor!WinMain() [d:\ue4deveditor\engine\source\runtime\launch\private\windows\launchwindows.cpp:210]
UE4Editor!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:253]
kernel32
ntdll