While debugging a publishing error in CX, I came across this error in parsoid
```
[fatal][enwiki/Miguel_Ángel_Menéndez] Cannot read property 'nodeValue' of null
TypeError: Cannot read property 'nodeValue' of null
at Normalizer.moveTrailingSpacesOut (/home/santhosh/dev/wiki/parsoid/lib/wts.normalizeDOM.js:218:24)
at Normalizer.normalizeNode (/home/santhosh/dev/wiki/parsoid/lib/wts.normalizeDOM.js:278:8)
at Normalizer.processNode (/home/santhosh/dev/wiki/parsoid/lib/wts.normalizeDOM.js:445:15)
at Normalizer.processSubtree (/home/santhosh/dev/wiki/parsoid/lib/wts.normalizeDOM.js:393:11)
at Normalizer.processNode (/home/santhosh/dev/wiki/parsoid/lib/wts.normalizeDOM.js:442:9)
at Normalizer.normalizeDOM (/home/santhosh/dev/wiki/parsoid/lib/wts.normalizeDOM.js:463:14)
at WikitextSerializer.WSP.serializeDOMSync (/home/santhosh/dev/wiki/parsoid/lib/mediawiki.WikitextSerializer.js:1357:26)
at WikitextSerializer.WSP.serializeHTML (/home/santhosh/dev/wiki/parsoid/lib/mediawiki.WikitextSerializer.js:92:40)
at WikitextSerializer.WSP._buildExtensionWT (/home/santhosh/dev/wiki/parsoid/lib/mediawiki.WikitextSerializer.js:634:24)
at Object.handle (/home/santhosh/dev/wiki/parsoid/lib/mediawiki.WikitextSerializer.js:701:30)
```
To reproduce, try the HTML in https://phabricator.wikimedia.org/P1905
The HTML to wikitext conversion works fine. If the conversion done with 'scrubWikitext' => 1, the above failure happens. CX uses 'scrubWikitext' => 1, setting.
The above error is from my local parsoid running master code(5fa1a9d8f8941d31502019baf950e608237efed1)