I'm currently building a form with React, and I'm wondering what the best practices are for pre-filling fields from an object.

```
import React, { Component } from 'react'

class EditResourceForm extends Component {
  constructor (props) {
    super(props)

    this.state = {
      resource: props.resource
    }
  }

  handleFieldChanged (e) {
    // update state
  }

  render () {
    return (
      <input
        type="text"
        value={this.state.resource.email}
        onChange={::this.handleFieldChanged} />
    )
  }
}

```

I'm encountering a problem when `this.state.resource.email` is null or undefined, because React does not want me providing those as values to controlled components:

```
Warning: `value` prop on `input` should not be null. Consider using the   
empty string to clear the component or `undefined` for uncontrolled    
components.

```

Where is the proper place to provide an empty string as a fallback for a `null` value? Should this be done in the parent component's constructor method? Is there a way to avoid having to do this explicitly for every attribute that might have a `null` value?