Stop sending null aggregatable debug report when there is no attribution
data in trigger registration
https://wicg.github.io/attribution-reporting-api/#trigger-attribution
step 2 early return in this case.
Bug: 352352899
Change-Id: Id8d2029c1d7668cafbc2e6dcb99cdc870c26b9d0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5689900
Reviewed-by: Andrew Paseltiner apaseltiner@chromium.org
Commit-Queue: Nan Lin linnan@chromium.org
Cr-Commit-Position: refs/heads/main@{#1326081}