Cannot read property 'toString' of null when using raw filter on a undefined variable

Created by: ofabel

The following template is supposed to work with strict mode disabled: https://twigfiddle.com/pumltd

Twing in Version 5.0.2 will throw the following exception:

TypeError: Cannot read property 'toString' of null
at raw (node_modules\twing\dist\cjs\lib\extension\core\filters\raw.js:11:35)
at node_modules\twing\dist\cjs\lib\callable-wrapper.js:46:29
...