Task: Handle errors from a different workflow

n8n workflow JSON:
{"nodes":[{"name":"Error Trigger","type":"n8n-nodes-base.errorTrigger","position":[250,500],"parameters":{},"typeVersion":1},{"name":"Mailgun","type":"n8n-nodes-base.mailgun","position":[450,500],"parameters":{"text":"=Error: {{$node[\"Error Trigger\"].data[\"execution\"][\"error\"][\"message\"]}}\n\nStack Trace:\n{{$node[\"Error Trigger\"].data[\"execution\"][\"error\"][\"stack\"]}}","subject":"=Workflow Error:  {{$node[\"Error Trigger\"].data[\"workflow\"][\"name\"]}}","toEmail":"","fromEmail":""},"credentials":{"mailgunApi":""},"typeVersion":1}],"connections":{"Error Trigger":{"main":[[{"node":"Mailgun","type":"main","index":0}]]}}}