Function `%||%` fails on R-devel due to `_R_CHECK_LENGTH_1_LOGIC2_`

[dschlaep]

R-devel introduces as new features:
"Experimentally, setting environment variable _R_CHECK_LENGTH_1_LOGIC2_ will lead to warnings (or errors if the variable is set to a ‘true’ value) when && or || encounter and use arguments of length more than one. " (https://cran.r-project.org/doc/manuals/r-devel/NEWS.html)

The lintr function %||% will fail this upcoming check, e.g.,

x <- c("", "", "object_name_linter", "", "", "", "", "", "", "", "")
y <- c("", "", "", "", "", "", "", "", "", "", "")
lintr:::`%||%`(x, y)

with message

Error in is.null(x) || is.na(x) : 
  'length(x) = 11 > 1' in coercion to 'logical(1)'

Expected result (as obtained with R v3.5.2):

> lintr:::`%||%`(x, y)
 [1] ""                   ""                  
 [3] "object_name_linter" ""                  
 [5] ""                   ""                  
 [7] ""                   ""                  
 [9] ""                   ""                  
[11] ""                  

Suggested fix: replace
if (is.null(x) || is.na(x) || length(x) <= 0) {...
with
if (is.null(x) || anyNA(x) || length(x) <= 0) {...
(anyNA was introduced in R v3.1.0 (https://cran.r-project.org/doc/manuals/r-release/NEWS.html) which is earlier than the lintr required R version 3.1.1).

[russHyde]

Ref #395

[russHyde]

Fixed in #395