Fix JSX syntax error in result card component

Fixed incomplete conditional expression after removing
duplicate content section. Added fallback message for
missing additional context.

client/src/components/knowledge-base/result-card.tsx

@@ -379,6 +379,11 @@ export default function ResultCard({
                       </span>
                     )}
                   </div>
+                ))}
+                {!document.additionalContext && (
+                  <p className="text-sm text-slate-600 dark:text-slate-400 italic">
+                    No additional context available.
+                  </p>
                 )}
               </div>
             </div>