fix(ai-chat): add null check to model name

When the OpenAI-compatible fallback (/v1/models) is used, models are mapped as { name: m.id, size: 0 } with no details field. Accessing model.details.parameter_size throws
TypeError: Cannot read properties of undefined, which crashes the React render and causes the entire page to go blank.

admin/inertia/pages/settings/models.tsx

@@ -369,7 +369,7 @@ export default function ModelsPage(props: {
                       </td>
                       <td className="px-4 py-3">
                         <span className="text-sm text-text-secondary">
-                          {model.details.parameter_size || 'N/A'}
+                          {model.details?.parameter_size || 'N/A'}
                         </span>
                       </td>
                       <td className="px-4 py-3">