`rds` feature confused by char vectors containing NAs

[brodieG]

Bug likely in:

if (is.chr.1L(x) && file_test("-f", x) || inherits(x, "connection"))

in get_rds, should be parenthesis around or statement.

[brodieG]

Can't reproduce this right now, tried with:

diffPrint(c(NA, "hell"), c(letters, NA))

Will have to track down the more complex example. Perhaps this is related:

> diffChr(c(NA, "hell"), c(letters, NA))
Error in if (any(nc_fun(cur.capt) > etc@text.width.half) || any(nc_fun(tar.capt) >  : 
  missing value where TRUE/FALSE needed