nla: invalidate sec handle after creation

If sec pointer isn't invalidated after creation it is not possible
to check if the upper and lower pointers are valid.

This fixes a segfault in the server part if the client disconnects before
the authentication was finished.
SECURITY_STATUS SEC_ENTRY InitializeSecurityContextW(PCredHandle phCredential, PCtxtHandle phContext,
		SEC_WCHAR* pszTargetName, ULONG fContextReq, ULONG Reserved1, ULONG TargetDataRep,
		PSecBufferDesc pInput, ULONG Reserved2, PCtxtHandle phNewContext,
		PSecBufferDesc pOutput, PULONG pfContextAttr, PTimeStamp ptsExpiry)
{
	SEC_CHAR* Name;
	SECURITY_STATUS status;
	SecurityFunctionTableW* table;

	Name = (SEC_CHAR*) sspi_SecureHandleGetUpperPointer(phCredential);

	if (!Name)
		return SEC_E_SECPKG_NOT_FOUND;

	table = sspi_GetSecurityFunctionTableWByNameA(Name);

	if (!table)
		return SEC_E_SECPKG_NOT_FOUND;

	if (table->InitializeSecurityContextW == NULL)
		return SEC_E_UNSUPPORTED_FUNCTION;

	status = table->InitializeSecurityContextW(phCredential, phContext,
			pszTargetName, fContextReq, Reserved1, TargetDataRep,
			pInput, Reserved2, phNewContext, pOutput, pfContextAttr, ptsExpiry);

	return status;
}

SECURITY_STATUS SEC_ENTRY InitializeSecurityContextW(PCredHandle phCredential, PCtxtHandle phContext,
		SEC_WCHAR* pszTargetName, ULONG fContextReq, ULONG Reserved1, ULONG TargetDataRep,
		PSecBufferDesc pInput, ULONG Reserved2, PCtxtHandle phNewContext,
		PSecBufferDesc pOutput, PULONG pfContextAttr, PTimeStamp ptsExpiry)
{
	SEC_CHAR* Name;
	SECURITY_STATUS status;
	SecurityFunctionTableW* table;

	Name = (SEC_CHAR*) sspi_SecureHandleGetUpperPointer(phCredential);

	if (!Name)
		return SEC_E_SECPKG_NOT_FOUND;

	table = sspi_GetSecurityFunctionTableWByNameA(Name);

	if (!table)
		return SEC_E_SECPKG_NOT_FOUND;

	if (table->InitializeSecurityContextW == NULL)
		return SEC_E_UNSUPPORTED_FUNCTION;

	status = table->InitializeSecurityContextW(phCredential, phContext,
			pszTargetName, fContextReq, Reserved1, TargetDataRep,
			pInput, Reserved2, phNewContext, pOutput, pfContextAttr, ptsExpiry);

	return status;
}
