Can't display France parameter cotsoc.sal.commun.assedic

[Morendil]

La https://fr.openfisca.org/legislation/cotsoc.sal.commun.assedic?q=assedic ne s'affiche pas à cause d'une erreur JS.

[Morendil]

This appears to have its root cause in Core's API implementation; the relevant rate comes to an end as of 2018-10-01, both rates and threshold are set to null at that date. The API represents this as a 2018-10-01 key containing a bracket having a value of null, and the client code chokes on that.