nassh: handle exception when no SKE exists

Tests such as terminal.SSH on the bots run without any SKE installed.

Change-Id: I6bfdd3791b34f6be45e8715ad740495d35300804
Reviewed-on: https://chromium-review.googlesource.com/c/apps/libapps/+/6712635
Reviewed-by: Jason Lin <lxj@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Yiyue Wang <yiyuew@google.com>
diff --git a/nassh/js/nassh_google.js b/nassh/js/nassh_google.js
index e93941e..16aa55e 100644
--- a/nassh/js/nassh_google.js
+++ b/nassh/js/nassh_google.js
@@ -119,7 +119,7 @@
     defaultSkeExtension, {
       type: 'get_ssh_policy_request',
       slot: gnubbySlot.CORP_NORMAL_CERT_SLOT,
-    });
+    }).catch((e) => ({}));
 
   const data = response['data'] ?? {};