fix(dashboard): Resolve chat preview undefined length error fixes NV-6280 (#8746)

Co-authored-by: Cursor Agent <[email protected]>

Author: scopsy

apps/dashboard/src/components/workflow-editor/steps/chat/chat-preview.tsx

@@ -15,7 +15,7 @@ export const ChatPreview = ({
   variant?: 'mini' | 'default';
 }) => {
   const isValidChatPreview =
-    previewData?.result.type === ChannelTypeEnum.CHAT && previewData?.result.preview.body.length > 0;
+    previewData?.result.type === ChannelTypeEnum.CHAT && previewData?.result.preview.body?.length > 0;
   const body = isValidChatPreview ? ((previewData?.result.preview as ChatRenderOutput)?.body ?? '') : '';
 
   return (