Handle blank issue IDs

test/fixtures/PAN-OS-9.1.11-h3-addressed/expected-parsed.json

@@ -0,0 +1,9 @@
+[
+  {
+    "id": "BLANK-000000",
+    "summary": "Fixed a Denial-of-Service (DoS) vulnerability in the GlobalProtect portal and gateway ([CVE-2021-3063](https://security.paloaltonetworks.com/CVE-2021-3063)).",
+    "resolved": "",
+    "caveat": "",
+    "renderedHtml": "<p>Fixed a Denial-of-Service (DoS) vulnerability in the GlobalProtect portal and gateway (<a href=\"https://security.paloaltonetworks.com/CVE-2021-3063\">CVE-2021-3063</a>).</p>\n"
+  }
+]