Fix: prevent Stripe Payment Element from rendering when amount is zero

[jonwaldstein]

Resolves GIVE-509

Description

This prevents the Stripe Payment Element from rendering when the donation amount is zero by adding a conditional before loading the fields.

Affects

Stripe payment element gateways

Visuals

Before:

After

Testing Instructions

• create a v3 form
• specify 0 for the amount
• click on stripe payment element

Pre-review Checklist

• [ ] Acceptance criteria satisfied and marked in related issue
• [ ] Relevant @unreleased tags included in DocBlocks
• [ ] Includes unit tests
• [ ] Reviewed by the designer (if follows a design)
• [ ] Self Review of code and UX completed