Documenting `NA` object does not provide useful error message

[1beb]

While documenting a package, I accidentally typed NA instead of NULL at the end of the roxygen block.

It was challenging to find my error, especially when using Build and Reload within RStudio (becuase there's no traceback)

Error: is.call(call) is not TRUE

Trying to roxygenize in the console allowed me to get the results of a traceback():

11: stop(sprintf(ngettext(length(r), "%s is not TRUE", "%s are not all TRUE"), 
        ch), call. = FALSE, domain = NA)
10: stopifnot(is.call(call))
9: standardise_call(call, env)
8: object_from_call(call, env, preref)
7: (function (call, ref, comment_ref) 
   {
       preref <- parse.preref(as.character(comment_ref))
       if (is.null(preref)) 
           return()
       preref$object <- object_from_call(call, env, preref)
       preref$srcref <- list(filename = file, lloc = as.vector(ref))
       add_defaults(preref)
   })(dots[[1L]][[1L]], dots[[2L]][[1L]], dots[[3L]][[1L]])
6: mapply(FUN = f, ..., SIMPLIFY = FALSE)
5: Map(extract, parsed, refs, comment_refs)
4: FUN(c("/home/path/to/package/file1.r", 
   "/home/path/to/package/file2.r", 
   .... # list of files truncated 
   "/home/path/to/package/doc.file.r")[[25L]], 
       ...)
3: lapply(r_files(base_path), parse_file, env = env)
2: parse_package(base_path, load_code)
1: roxygenize("~/Current/r/path/to/package/")