Error loading mapview package


I installed mapview package on my R studio and when I try to open it it doesn't works...
That's the message :

Erreur : package or namespace load failed for ‘mapview’:
.onLoad a échoué dans loadNamespace() pour 'units', détails :
appel : udunits_init(file.path(.get_ud_xml_dir(), "udunits2.xml"))
erreur : Error in function udunits_init: Can't open installed, default, unit database

Did someone get an idea?

Thank you very much,