Skip rawPart append when bailing out on null token

Author: lacatoire

packages/guides-restructured-text/src/RestructuredText/Parser/Productions/InlineRules/TextRoleRule.php

@@ -76,12 +76,12 @@ public function apply(BlockContext $blockContext, InlineLexer $lexer): InlineNod
 
                     break;
                 case InlineLexer::BACKSLASH:
-                    $rawPart .= $token->value;
                     $lexer->moveNext();
                     if ($lexer->token === null) {
                         break 2;
                     }
 
+                    $rawPart .= $token->value;
                     $part .= $lexer->token->value;
                     $rawPart .= $lexer->token->value;