Bug in makeNiceTif

[bwcompton]

In some circumstances, variable a at line 188 is undefined. This happens when usesf is FALSE and the destination file isn't created.

if (usesf) {
    opts <- character(0)
    ...
    do.call(sf::gdal_utils, args = args)
}
else {
    ...
    a <- system(command = command, intern = TRUE, wait = TRUE)
}
if (!file.exists(destination)) 
    stop("Output file", destination, "was not created. System call returned: ", 
        a)