EXC_BREAKPOINT — dispatch_assert_queue_fail

Empty completionHandler closure inferred @MainActor by Swift 6, but called on com.apple.launchservices.open-queue. Starting with Sequoia, AppKit began enforcing that expectation with dispatch_assert_queue.

Remove the completionHandler parameter entirely. No closure, no annotation, no assertion.

Tip jar sheet appears empty during App Store review. No products, no error message.

Product.products(for:) returns [] when the Paid Apps Agreement in App Store Connect is not active. No agreement, no products in the sandbox.

Detect empty array, show explanatory message instead of a blank sheet.