Just prevent `TypeError: Cannot read property 'constructor' of undefined`

[jasonxia23]

Just prevent TypeError: Cannot read property 'constructor' of undefined

[coveralls]

Coverage remained the same at 93.617% when pulling c7a989eb051ccf6e8eda27dde48ee10dbce401f9 on jasonxia23:master into 531cb127308b41f20f3b0c1f3b4df0027bceca21 on huei90:master.

[liorcode]

please update both the sources and create the dist and minified dist files using the build task and squash your commits.

But I actually think the solution should be in the checkValidation function itself.. I think it should always return either error or success, never undefined. This is my proposal: #241

[hueitan]

yes, there is no undefined return.