PaymentRequest: Remove unnecessary code

The hasError() method is already calling IsNull() internally.
Also, the error field in mojom has a default value as empty string.

Bug: none
Change-Id: I98edd7c11a32379cc477b3f0520b3293b83a9009
Reviewed-on: https://chromium-review.googlesource.com/1239294
Reviewed-by: Rouslan Solomakhin <rouslan@chromium.org>
Commit-Queue: Jinho Bang <jinho.bang@samsung.com>
Cr-Commit-Position: refs/heads/master@{#593560}
1 file changed