[RFR] Fix undefined issue in asyncValidation for SelectInput

[erkimii]

Property with undefined value was passed to asyncValidation when onBlur event occured

[fzaninotto]

Sorry, I fail to understand the bug you're solving, can you show some example code, and the error you get?

[erkimii]

@fzaninotto
Steps to reproduce:

• Have an asyncValidated form with <SelectInput source="a" choices={[ id: 'b', name: 'Only choice' ]} />
• Change value in the input a
• Debug data (first argument) passed to asyncValidate method

When validation is called on input change, then data equals { a: 'b' }
When validation is called on input blur, then data equals { a: undefined }

This bug is created by #2203
If you look closely, there is value passed for onBlur in SelectArrayInput but not for SelectInput

[fzaninotto]

Thanks, then!