Fixing build issue related to new "na.print" argument in data.table

[joshhwuu]

Thanks Toby @tdhock for bringing this to my attention via issue in data.table.

Recently, a new argument was added to print.data.table, which affected re-building of vignettes, as outlined in the original issue. Credit to @MichaelChirico for the find; the issue was here:

TrialEmulation/R/generics.R

Line 50 in 989f064

print(data.table(data = object$data), topn = 3, n = 5, col.names = "none", ...)

With the new na.print argument, n = 5 is no longer partially matched to nrows, so the change is trivial. I've also gone ahead and taken a quick look at other function calls that could avoid partial matching in its arguments, and changed those as well.

[gravesti]

Thanks @joshhwuu for this PR and apologies I didn't notice it earlier. Will update on CRAN as soon as possible