When opening a save file made with a previous version of the mod, there was an error message about line 42 of event.lua. I was able to fix this by changing that line from
<pre>
log("Detected mod update for mod "..mod_name..", old version '"..mod_version"', new version '"..new_version"'.")
</pre>
to
<pre>
log("Detected mod update for mod "..mod_name..", old version '"..mod_version.."', new version '"..new_version.."'.")
</pre>
