fix: fix render undefined when text children is empty (#19135)

web/app/components/base/markdown.tsx

 // visit https://reactjs.org/docs/error-decoder.html?invariant=185 for the full message
 // or use the non-minified dev environment for full errors and additional helpful warnings.
 
-const CodeBlock: any = memo(({ inline, className, children, ...props }: any) => {
+const CodeBlock: any = memo(({ inline, className, children = '', ...props }: any) => {
   const { theme } = useTheme()
   const [isSVG, setIsSVG] = useState(true)
   const match = /language-(\w+)/.exec(className || '')
     const { onSend } = useChatContext()
     const hidden_text = decodeURIComponent(node.properties.href.toString().split('abbr:')[1])
 
-    return <abbr className="cursor-pointer underline !decoration-primary-700 decoration-dashed" onClick={() => onSend?.(hidden_text)} title={node.children[0]?.value}>{node.children[0]?.value}</abbr>
+    return <abbr className="cursor-pointer underline !decoration-primary-700 decoration-dashed" onClick={() => onSend?.(hidden_text)} title={node.children[0]?.value || ''}>{node.children[0]?.value || ''}</abbr>
   }
   else {
     return <a {...props} target="_blank" className="cursor-pointer underline !decoration-primary-700 decoration-dashed">{children || 'Download'}</a>