I've gone through the code and I can see where these 2 errors could occur - it is when the /setlanguage command is used without the correct correct format.
I will work on making the extension more robust around this code at some point soon.
The fix is to close Fantasy Grounds, edit the db.xml file in your campaign folder and delete any blank <id-XXXXX> entries from the <language_extension> section.
Make a copy of your campaign db.xml file before modifying it! (Just in case).
For example, the following has a problem <id-00002> entry:
Code:
<language_extension>
<id-00001>
<fontname type="string">osiriani</fontname>
<languagename type="string">egyptian</languagename>
</id-00001>
<id-00002>
</id-00002>
</language_extension>
Delete <id-00002> and the closing tag </id-00002> to give:
Code:
<language_extension>
<id-00001>
<fontname type="string">osiriani</fontname>
<languagename type="string">egyptian</languagename>
</id-00001>
</language_extension>
Save db.xml and load your campaign. You should be able to use /listlanguages and /setlanguage without errors now. But, make sure you use /setlanguage correctly (until I update the extension to stop this issue) otherwise this error may occur again.