Invalid access to memory - Vcl::Comctrls::TTreeNode::SetImageIndex

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WinSCP 6.3.6

Error message:
Invalid access to memory.

Stack trace:
(0043ABB8) Vcl::Comctrls::TTreeNode::SetImageIndex
(0009909F) ntdll.dll
(00078371) ntdll.dll.KiUserExceptionDispatcher
(004A1F4D) Driveview::TDriveView::InternalWndProc
(00226F74) System::Classes::_18201
(00032471) USER32.dll
(00023231) USER32.dll
(00021A43) USER32.dll
(000215AB) USER32.dll.DispatchMessageW

The problem happens rarely. I cannot reproduce it.