[BUGFIX] Fix extension scanner Index.rst filename parsing

Rst files may not contain issue numbers. The extension scanner
iterates all .rst files (including Index.rst) which cases a type
error for typo3/sysext/core/Documentation/Changelog/7.0/Index.rst

(1/1) TypeError
Return value of
TYPO3\CMS\Install\UpgradeAnalysis\DocumentationFile::parseIssueId()
must be of the type string, null returned

Releases: master, 9.5
Resolves: #91027
Related: #90923
Change-Id: I000675700f9da17f063ccbc52d6ce0beabebf247
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64161


Tested-by: Josef Glatz <josefglatz@gmail.com>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Josef Glatz <josefglatz@gmail.com>
Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>

typo3/sysext/install/Classes/UpgradeAnalysis/DocumentationFile.php

@@ -154,10 +154,10 @@ class DocumentationFile
                 $entry['filename']
             );
         }
-        $entry['url']['issue'] = sprintf(
-            'https://forge.typo3.org/issues/%s',
-            $this->parseIssueId($entry['filename'])
-        );
+        $issueId = $this->parseIssueId($entry['filename']);
+        if ($issueId) {
+            $entry['url']['issue'] = sprintf('https://forge.typo3.org/issues/%s', $issueId);
+        }
 
         return [md5($file) => $entry];
     }
@@ -349,11 +349,11 @@ class DocumentationFile
     /**
      * @param string $filename
      *
-     * @return string
+     * @return string|null
      */
-    protected function parseIssueId(string $filename): string
+    protected function parseIssueId(string $filename): ?string
     {
-        return GeneralUtility::trimExplode('-', $filename)[1];
+        return GeneralUtility::trimExplode('-', $filename)[1] ?? null;
     }
 
     /**

typo3/sysext/install/Resources/Private/Partials/Upgrade/UpgradeDocs/PanelItem.html

@@ -29,7 +29,9 @@
     <div id="collapse{id}" class="panel-collapse collapse" role="tabpanel" aria-labelledby="heading{id}">
         <div class="rst-tags t3js-tags"></div>
         <div class="rst-links">
-            <a href="{fileArray.url.issue}" target="_blank" rel="noreferrer" class="nowrap"><core:icon identifier="actions-window-open" /> Open issue</a>
+            <f:if condition="{fileArray.url.issue}">
+                <a href="{fileArray.url.issue}" target="_blank" rel="noreferrer" class="nowrap"><core:icon identifier="actions-window-open" /> Open issue</a>
+            </f:if>
             <f:if condition="{fileArray.url.documentation}">
                 <a href="{fileArray.url.documentation}" target="_blank" rel="noreferrer" class="nowrap"><core:icon identifier="actions-window-open" /> Open rendered version</a>
             </f:if>