Did you apply the patch? If you applied it the same empty string warning can't keep happening.
Please do the following tests:
· Try to run the included samples of the method in the examples folder.
· Resave one your DOCX template using MS Word and try again.
· Send one of your DOCX to contact[at]phpdocx.com
If Google Docs doesn't include some important files, additional checks could be needed to use the native HTML to DOCX transformation with that files.