Squiz/ScopeKeywordSpacing: add more defensive coding

When the sniff would encounter a parse error/be run during live coding, the sniff could trigger an `Undefined array key` notice for the use of `$stackPtr + 2`.

Fixed now by bowing out early if the keyword is found at the end of a file.

Includes additional tests.

Author: jrfnl

src/Standards/Squiz/Sniffs/WhiteSpace/ScopeKeywordSpacingSniff.php

@@ -127,6 +127,9 @@ public function process(File $phpcsFile, $stackPtr)
 
         if ($tokens[($stackPtr + 1)]['code'] !== T_WHITESPACE) {
             $spacing = 0;
+        } else if (isset($tokens[($stackPtr + 2)]) === false) {
+            // Parse error/live coding. Bow out.
+            return;
         } else {
             if ($tokens[($stackPtr + 2)]['line'] !== $tokens[$stackPtr]['line']) {
                 $spacing = 'newline';

src/Standards/Squiz/Tests/WhiteSpace/ScopeKeywordSpacingUnitTest.2.inc

@@ -0,0 +1,6 @@
+<?php
+
+// Intentional parse error.
+// Testing that the sniff does not throw an "Undefined array key" notice during live coding.
+// This must be the only test in this file.
+readonly

src/Standards/Squiz/Tests/WhiteSpace/ScopeKeywordSpacingUnitTest.3.inc

@@ -0,0 +1,6 @@
+<?php
+
+// Intentional parse error.
+// Testing that the sniff still adds a space when there is only a comment after the keyword during live coding.
+// This must be the only test in this file.
+readonly/*comment*/

src/Standards/Squiz/Tests/WhiteSpace/ScopeKeywordSpacingUnitTest.3.inc.fixed

@@ -0,0 +1,6 @@
+<?php
+
+// Intentional parse error.
+// Testing that the sniff still adds a space when there is only a comment after the keyword during live coding.
+// This must be the only test in this file.
+readonly /*comment*/

src/Standards/Squiz/Tests/WhiteSpace/ScopeKeywordSpacingUnitTest.php

@@ -58,6 +58,9 @@ public function getErrorList($testFile='')
                 140 => 3,
             ];
 
+        case 'ScopeKeywordSpacingUnitTest.3.inc':
+            return [6 => 1];
+
         default:
             return [];
         }//end switch