[Django]-Provide default value for optional field in Django model

blank=True is not the same as null=True, as the documentation explains. When a text field is blank, it still needs some kind of value: but that value can be the empty string.

So, just select option 1, and enter '' as the default value.

There is a ticket created for this behavior for Django 1.7.
Take a look here

You need to use default="".