throw event error

[xiaomingming]

It's my gulp config:

var gulp = require('gulp');
require('gulp-grunt')(gulp,{
    base: './',
    prefix: 'grunt-',
    verbose: false
});
gulp.task('tpl', function() {
    return gulp.start('grunt-tpl');
});

when i execute gulp tpl,my console throw event error:

$ gulp tpl
[18:36:26] Using gulpfile f:\A_local\vipMobile\gulpfile.js
[18:36:26] Starting 'tpl'...
[18:36:26] Starting 'grunt-tpl'...
[18:36:26] Finished 'tpl' after 4.99 ms
events.js:141
      throw er; // Unhandled 'error' event
      ^

Error: spawn .//grunt.cmd ENOENT
    at exports._errnoException (util.js:874:11)
    at Process.ChildProcess._handle.onexit (internal/child_process.js:178:32)
    at onErrorNT (internal/child_process.js:344:16)
    at doNTCallback2 (node.js:439:9)
    at process._tickCallback (node.js:353:17)
    at Function.Module.runMain (module.js:469:11)
    at startup (node.js:134:18)
    at node.js:961:3

But,grunt tpl run well.

[xiaomingming]

Well,base should set null.It's my config problem.