KML files cause error on display

KML format is not directly supported in the Geofield ( https://www.drupal.org/project/geofield → ) and Leaflet ($this) modules, hence I assume you are referring to a user scenario where the Geocoder module ( https://www.drupal.org/project/geocoder → ) is being used to transform a KML file into a Geofield (WKT or GeoJson), throughout the KML Geocoder provided.

Well ... all looks good to me (and no sign or log of that error you report), also in the Geocoder module scenario and with Drupal Leaflet 10.2.45, as you can see in the attached screenshot where the attached simple.kml file is being geocoded into a Geofield field ...

Anyway ... the error message that you describe looks similar to/ identical to the one reported also in this other issue) still related to Leaflet release 10.2.45 ...: https://www.drupal.org/project/leaflet/issues/3521371 🐛 Version 10.2.45 introduces a bug with Views tooltips. Active

Could you please QA and Review the patch attached in comment #2 in that Issue thread here (?):
https://www.drupal.org/project/leaflet/issues/3521371#comment-16087181 🐛 Version 10.2.45 introduces a bug with Views tooltips. Active
and let us know if that eventually fixes this issue on your side?

Thanks!

Please also test new Leaflet 10.2.46 release → and check if that new release also fixes this issue.