Looking into this further, it looks like there may be an error or omission in
/YOUR_ADMIN/includes/modules/sitemapxml_install.php
I am not receiving this error, but I am receiving a similar error that TABLE_SITEMAPXML_EXTRAURLS is not defined.
One thing I did find is that on line 24 and 25, it appears that SITEMAPXML_CHECK_DUPLICATES is spelled SITEMAPXML_CHECK_DUBLICATES (note the "B" instead of the "P"). I don't know if this is the cause of the error, or if it is even actually an error.
However, this file appears to both define the variables you are running into errors with, and be the only references I am finding to those variable names...
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