When testing with modal true, jest test fails with "Cannot read properties of null (reading 'openPicker')"

[Ryan-Durling]

Describe the bug
When testing with jest and setting modal to true it throws an exception.

Cannot read properties of null (reading 'openPicker')
TypeError: Cannot read properties of null (reading 'openPicker')
    at DatePickerAndroid.openPicker [as render] 

Expected behavior
A clear and concise description of what you expected to happen.

renders without error in jest test

To Reproduce
Add example code that reproduces the behavior.

it('does something') {
    render(<DatePicker
        modal={true}
        ... other props ...
      />)

        ... the rest of the test...
}

Smartphone (please complete the following information):

• OS: [Android or iOS]
• React Native version [e.g. 0.59.4]
• react-native-date-picker version [e.g. 2.5.1]

[henninghall]

See #423