Range check error - IsUnixHiddenFile

<Try to describe precise steps that lead to the problem (where do you click, what keys do you press, what do you see, etc.)>
<If relevant, consider attaching a session log file or a screenshot)>

WinSCP 6.3.6

Error message:
Range check error

Stack trace:
(00E253C1) C6612_3
(00E268F4) _ThrowExceptionLDTC
(00B818EE) IsUnixHiddenFile
(00491887) Customdriveview::TCustomDriveView::InternalOnDrawItem
(004401A0) Vcl::Comctrls::TCustomTreeView::CustomDrawItem
(00492711) Customdriveview::TCustomDriveView::CustomDrawItem
(0043EC07) Vcl::Comctrls::TCustomTreeView::CNNotify
(0049283D) Customdriveview::TCustomDriveView::CNNotify
(00409029) Vcl::Controls::TWinControl::WndProc
(0043F396) Vcl::Comctrls::TCustomTreeView::WndProc
(0040918F) Vcl::Controls::_17076
(00409029) Vcl::Controls::TWinControl::WndProc
(00408670) Vcl::Controls::TWinControl::MainWndProc
(00226F74) System::Classes::_18201
(00032431) USER32.dll
(00023231) USER32.dll
(00022CB5) USER32.dll
(0002CC1D) USER32.dll
(0007816B) ntdll.dll.KiUserCallbackDispatcher
(00038BB3) USER32.dll
(00021D11) USER32.dll.SendMessageW
(00099EF6) COMCTL32.DLL
(0004BF29) COMCTL32.DLL
(00048FF9) COMCTL32.DLL
(0006DD17) COMCTL32.DLL
(00049CB9) COMCTL32.DLL
(00032431) USER32.dll
(00023231) USER32.dll
(00022BA2) USER32.dll.CallWindowProcW
(0040913A) Vcl::Controls::TWinControl::DefaultHandler
(0040D4A3) Vcl::Controls::TWinControl::WMPrintClient
(00AEF452) TCustomUnixDriveView::Dispatch
(00409029) Vcl::Controls::TWinControl::WndProc
(0043F396) Vcl::Comctrls::TCustomTreeView::WndProc
(00409A63) Vcl::Controls::TWinControl::WMPaint
(00AEF452) TCustomUnixDriveView::Dispatch
(00409029) Vcl::Controls::TWinControl::WndProc
(0043F396) Vcl::Comctrls::TCustomTreeView::WndProc
(00226F74) System::Classes::_18201
(00032431) USER32.dll
(00023231) USER32.dll
(00022BA2) USER32.dll.CallWindowProcW
(004C2D33) Dragdrop::TDragDrop::WndMethod
(00226F74) System::Classes::_18201
(00032431) USER32.dll
(00023231) USER32.dll
(00022CB5) USER32.dll
(0002CC1D) USER32.dll
(0007816B) ntdll.dll.KiUserCallbackDispatcher
(0004ED16) COMCTL32.DLL
(0004E670) COMCTL32.DLL
(0004A02C) COMCTL32.DLL
(00032431) USER32.dll
(00023231) USER32.dll
(00022BA2) USER32.dll.CallWindowProcW
(0040913A) Vcl::Controls::TWinControl::DefaultHandler
(00409029) Vcl::Controls::TWinControl::WndProc
(0043F396) Vcl::Comctrls::TCustomTreeView::WndProc
(00226F74) System::Classes::_18201
(00032431) USER32.dll
(00023231) USER32.dll
(00022BA2) USER32.dll.CallWindowProcW
(004C2D33) Dragdrop::TDragDrop::WndMethod
(00226F74) System::Classes::_18201
(00032431) USER32.dll
(00023231) USER32.dll
(00022CB5) USER32.dll
(0002CC1D) USER32.dll
(0007816B) ntdll.dll.KiUserCallbackDispatcher
(00038BB3) USER32.dll
(00021D11) USER32.dll.SendMessageW

The problem happens rarely. I cannot reproduce it.