Fix GiftedForm child is null error.

[cnjon]

...
    <GiftedForm.SeparatorWidget />
                {this.state.isShowSwitch && (
                    <GiftedForm.SwitchWidget
                        name="test"
                        title="test"
                        image={<IconIon  name="lightbulb" />}
                    />
                )}
                <GiftedForm.SeparatorWidget />
...

If this.state.isShowSwitch is false,will throw an exception!

[FaridSafi]

Thank you @cnjon