Fix handling of first-time builds, when dist/deploy-old does not exist.

@@ -567,7 +567,7 @@ module.exports = function (grunt) {
             fs.symlinkSync(target, 'dist/next-current');
             fs.renameSync('dist/next-current', 'dist/current');
             if (current) {
-                if (fs.statSync('dist/deploy-old')) {
+                if (fs.existsSync('dist/deploy-old')) {
                     grunt.file.delete('dist/deploy-old');
                 }
                 fs.renameSync('dist/' + current, 'dist/deploy-old');