[Auth UI] Clear error message when switch between phone and email login

[joyzoursky]

When switching between phone and email login, error message will always persist on the screen, which is better to be cleared when switching the login method.

• Skygear Server Date/Version: Not sure
• Application Platform: Testing on client app

Expected Results

Should clear the error message when switch between phone and email login

Actual Results

See error message for phone number field still exist after switching to email login.

Steps to reproduce

1. Click Connect Phone or Email
2. Click Next directly
3. See required field error message
4. Click Use phone number / email instead button
5. See the error message still there