[Webportal] Fix job clone bug

[abuccts]

Fix job clone bug.

[coveralls]

Coverage remained the same at 53.345% when pulling a40fd0a on xiongyf/fix-job-clone into ef6a46c on master.

[coveralls]

Coverage increased (+0.01%) to 53.356% when pulling 3b12b40 on xiongyf/fix-job-clone into ef6a46c on master.

[Binyang2014]

Looks good to me.
But how about quick return when pluginId is Nil. More easy to understand?

if (isNil(pluginId)) {
  window.location.href = `/submit.html?${qs.stringify(query)}`;
  return;
}

const plugins = window.PAI_PLUGINS;
const pluginIndex = plugins.findIndex((x) => x.id === pluginId);
if (pluginIndex === -1) {
    alert(`Clone job failed. The job was submitted by ${pluginId}, but it is not installed.`);
    return;
}
window.location.href = `/plugin.html?${qs.stringify({...query, index: pluginIndex})}`;