[Poly > Mkdirp] Cleanup a bit

polyfills/mkdirp.js

@@ -2,15 +2,13 @@
 const fs = require('fs');
 
 const mk = (path, callback) => { // async
-  fs.mkdir(path, { recursive: true }, () => { // Already exists, ignore
+  fs.mkdir(path, { recursive: true }, () => callback()); // Never error
-    callback();
-  });
 };
 
 mk.sync = (path) => { // sync
   try {
     fs.mkdirSync(path, { recursive: true });
-  } catch (e) { } // Already exists, ignore
+  } catch (e) { } // Never error
 };
 
 module.exports = mk;