Uncaught TypeError: Cannot read property 'toString' of null (HelloWorld.js:106)

Example : https://paste.apache.org/yizbj
Select Date and click save button then validateFormOnServer function will be called.In that function we are doing
```
var date1:String = cc_AthrzDate.value.toString();
var date2:String = cc_CanclDate.value.toString();
```
cc_AthrzDate is mx:DateField.
cc_AthrzDate.value.toString(); is throwing exception because **cc_AthrzDate.value** is null

Please check this example

Start with the validateFormOnServer function and the mx:DateField values shown in the issue, then reproduce the flow by selecting a date and clicking Save. Check how the null value reaches the generated HelloWorld.js at line 106; done means the example no longer throws the TypeError during validation.

Written by the indexing model from the issue text.