RX Flex 레이아웃 '게시물 상단에 썸네일 표시' 기능 사용시 게시판 설정 접속 에러 'Error #0 ~ thumbnailExists() on null' 수정 방법'

<include target="components/board-thumbnail/board-thumbnail.html" />

            <!--@if($act == 'dispBoardAdminBoardInfo')-->
            <!--@elseif($act == 'dispBoardAdminCategoryInfo')-->
            <!--@elseif($act == 'dispBoardAdminExtraVars')-->
            <!--@elseif($act == 'dispBoardAdminGrantInfo')-->
            <!--@elseif($act == 'dispBoardAdminBoardAdditionSetup')-->
            <!--@elseif($act == 'dispBoardAdminSkinInfo')-->
            <!--@elseif($act == 'dispBoardAdminMobileSkinInfo')-->
            <!--@else-->
            <include target="components/board-thumbnail/board-thumbnail.html" />
            <!--@end-->