Invalid access to memory - TLoginDialog::AddLoginButtonImage

<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 6.5.4

Error message:
Invalid access to memory.

Stack trace:
(00036E4E) apphelp.dll
(0008818F) ntdll.dll
(00074711) ntdll.dll.KiUserExceptionDispatcher
(00DAD19D) TLoginDialog::AddLoginButtonImage
(00DAC7E8) TLoginDialog::UpdateLoginButton
(00DB0592) TLoginDialog::ActionListUpdate
(00221920) System::Actions::TContainedActionList::UpdateAction
(0038ADA1) Vcl::Actnlist::TCustomAction::Update
(004ACF22) Vcl::Forms::_16859
(004ACF22) Vcl::Forms::_16859
(004ACF93) Vcl::Forms::TCustomForm::UpdateActions
(004B29EA) Vcl::Forms::TApplication::DoActionIdle
(004B1B9F) Vcl::Forms::TApplication::HandleMessage
(00DB0AD0) TLoginDialog::Execute
(00121243) GetLoginData
(000CE441) TTerminalManager::NewSession
(000252CC) TCustomScpExplorerForm::NeedSession
(0005B8BF) TScpCommanderForm::NeedSession
(00025244) TCustomScpExplorerForm::LastTerminalClosed
(000CB0D3) TTerminalManager::FreeTerminal
(000CA38F) TTerminalManager::FreeActiveTerminal
(000CAE23) TTerminalManager::ReconnectActiveTerminal
(000E0B38) ShowExtendedExceptionEx
(000269DC) TCustomScpExplorerForm::ShowExtendedException
(000CC5E5) TTerminalManager::TerminalShowExtendedException
(00D35F08) TTerminal::ShowExtendedException
(004B2022) Vcl::Forms::TApplication::HandleException
(00204C90) System::Classes::_18364
(00040459) USER32.dll
(00036B45) USER32.dll
(000353EB) USER32.dll
(00034F1B) USER32.dll.DispatchMessageW

The problem happens rarely. I cannot reproduce it.