dcc_inconsistent fails when columns are of type IDate

[danalvarez]

Problem

The dcc_inconsistent function fails when the date columns to compare are of type IDate.

How to reproduce

Call the function with an EIR with date columns of type IDate.

Error

The function returns this error:

Error in `mutate()`:
ℹ In argument: `diff = .data[["date_vax"]] - .data[["date_birth"]]`.
Caused by error:
! Internal error in -.IDate: storage mode of IDate is somehow no longer integer. Please report to the data.table issues tracker.