fix(DocComment): Fix undefined string index on short comments (#3307937)

coder_sniffer/Drupal/Sniffs/Commenting/DocCommentSniff.php

@@ -224,7 +224,8 @@ class DocCommentSniff implements Sniff
         // Remove any trailing white spaces which are detected by other sniffs.
         $shortContent = trim($shortContent);
 
-        if (preg_match('|\p{Lu}|u', $shortContent[0]) === 0
+        if ($shortContent !== ''
+            && preg_match('|\p{Lu}|u', $shortContent[0]) === 0
             // Allow both variants of inheritdoc comments.
             && $shortContent !== '{@inheritdoc}'
             && $shortContent !== '{@inheritDoc}'

tests/Drupal/bad/BadUnitTest.php

@@ -27,6 +27,11 @@ class BadUnitTest extends CoderSniffUnitTest
     protected function getErrorList(string $testFile): array
     {
         switch ($testFile) {
+        case 'bad_crlf.inc':
+            return [
+                1 => 2,
+                8 => 1,
+            ];
         case 'bad.css':
             return [
                 1  => 1,

tests/Drupal/bad/bad_crlf.inc

+<?php
+namespace Drupal\example\Controller;
+
+/**
+ * Foo.
+ */
+class ExampleController
+{
+
+}

tests/Drupal/bad/bad_crlf.inc.fixed

+<?php
+
+namespace Drupal\example\Controller;
+
+/**
+ * Foo.
+ */
+class ExampleController {}