Handle blank issue IDs

test/fixtures/PAN-OS-9.1.11-h3-addressed/input.html

@@ -0,0 +1,29 @@
+<table class="table colsep rowsep  table-striped">
+   <!--cq:include script="../../common/tablestack.jsp" /-->
+   <colgroup>
+      <col style="width: 50.0%">
+      <col style="width: 50.0%">
+   </colgroup>
+   <thead class="thead" data-sticky-top="62" style="top: 62px;">
+      <tr class="row rowsep">
+         <th class="entry">
+            <div class="p"><b class="ph b">Issue ID</b></div>
+         </th>
+         <th class="entry">
+            <div class="p"><b class="ph b">Description</b></div>
+         </th>
+      </tr>
+   </thead>
+   <tbody class="tbody">
+      <tr class="row">
+         <td class="entry">
+            <div class="p"><b class="ph b">—</b></div>
+         </td>
+         <td class="entry relcol">
+            <div class="p">Fixed a Denial-of-Service (DoS) vulnerability
+               in the GlobalProtect portal and gateway (<a class="xref" href="https://security.paloaltonetworks.com/CVE-2021-3063" title="" data-scope="external" data-format="html" data-type="" target="_blank">CVE-2021-3063</a>).
+            </div>
+         </td>
+      </tr>
+   </tbody>
+</table>