Performance/CacheValueOverride: add some more defensive coding

... to guard against the sniff throwing PHP notices/warnings due to parse errors/live coding.

Any such PHP notice/warning stops the PHPCS run for a file, so should be avoided.

Includes tests.

Author: jrfnl

WordPressVIPMinimum/Sniffs/Performance/CacheValueOverrideSniff.php

@@ -101,14 +101,16 @@ public function process_matched_token( $stackPtr, $group_name, $matched_content
 
 		$rightAfterNextVariableOccurence = $this->phpcsFile->findNext( Tokens::$emptyTokens, $nextVariableOccurrence + 1, $searchEnd, true, null, true );
 
-		if ( $this->tokens[ $rightAfterNextVariableOccurence ]['code'] !== T_EQUAL ) {
+		if ( $rightAfterNextVariableOccurence === false
+			|| $this->tokens[ $rightAfterNextVariableOccurence ]['code'] !== T_EQUAL
+		) {
 			// Not a value override.
 			return;
 		}
 
 		$valueAfterEqualSign = $this->phpcsFile->findNext( Tokens::$emptyTokens, $rightAfterNextVariableOccurence + 1, $searchEnd, true, null, true );
 
-		if ( $this->tokens[ $valueAfterEqualSign ]['code'] === T_FALSE ) {
+		if ( $valueAfterEqualSign !== false && $this->tokens[ $valueAfterEqualSign ]['code'] === T_FALSE ) {
 			$message = 'Obtained cached value in `%s` is being overridden. Disabling caching?';
 			$data    = [ $variableName ];
 			$this->phpcsFile->addError( $message, $nextVariableOccurrence, 'CacheValueOverride', $data );

WordPressVIPMinimum/Tests/Performance/CacheValueOverrideUnitTest.3.inc

@@ -0,0 +1,6 @@
+<?php
+
+// Parse error/live coding test.
+// This should be the only test in the file.
+$liveCoding = wp_cache_get();
+$liveCoding

WordPressVIPMinimum/Tests/Performance/CacheValueOverrideUnitTest.4.inc

@@ -0,0 +1,6 @@
+<?php
+
+// Parse error/live coding test.
+// This should be the only test in the file.
+$liveCoding = wp_cache_get();
+$liveCoding =