added fs.existsSync() before fs.statSync() to address crash caused by broken symlinks in node_modules

Author: benholloway

lib/build/node-sass.js

@@ -46,7 +46,7 @@ function encodeRelativeURL(startPath, uri) {
         return path.join(basePath, filename);
       })
       .filter(function directoriesOnly(absolutePath) {
-        return fs.statSync(absolutePath).isDirectory();
+        return fs.existsSync(absolutePath) && fs.statSync(absolutePath).isDirectory();
       })
       .filter(function notInRootPath(absolutePath) {
         return (pathToRoot.indexOf(absolutePath) < 0);