StringLiteral: only variables should be passed by reference.

[dantleech]

                                                             
  [Symfony\Component\Debug\Exception\ContextErrorException]  
  Notice: Only variables should be passed by reference       
                                                             

Exception trace:
 () at /home/daniel/www/phpactor/phpactor/vendor/microsoft/tolerant-php-parser/src/Node/StringLiteral.php:33
 Microsoft\PhpParser\Node\StringLiteral->getStringContentsText() at /home/daniel/www/phpactor/phpactor/vendor/phpactor/worse-reflection/lib/Core/Reflection/Inference/NodeValueResolver.php:105
 Phpactor\WorseReflection\Core\Reflection\Inference\NodeValueResolver->_resolveNode() at /home/daniel/www/phpactor/phpactor/vendor/phpactor/worse-reflection/lib/Core/Reflection/Inference/Node

Triggered when StringLitreal passes the method call fileGetContents to the getFullText of a Token object, which unlike the Node object accepts a reference.