fix(dashboard): handle the Properties stat failure instead of leaving it unhandled

puter.fs.stat both calls the error callback and rejects. The properties
dialog rendered the error from the callback but dropped the promise, so
opening it on a deleted item or offline logged an unhandled rejection.

src/gui/src/UI/Dashboard/UIItemPropertiesModal.js

@@ -289,7 +289,9 @@ export default function UIItemPropertiesModal ({ name, path: item_path, uid, $co
             if ( closed ) return;
             $list.html(`<div class="item-props-empty">${i18n('error_unknown_cause')}</div>`);
         },
-    });
+    })
+        // The error callback renders the failure; the promise rejects with it too.
+        .catch(() => {});
 
     return { close };
 }