[ios] Hide the cancel button when the initial text length is 0

Hide the rightView when the title of a group is empty.

This is a follow-up CL for https://chromium-review.googlesource.com/c/chromium/src/+/5822782 since the CL didn't
cover all cases of this issue.

Bug: 358653601
Change-Id: I2ee186b2df357bef78d2b31911a40b3fc4a83f94
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5928943
Reviewed-by: Louis Romero <lpromero@google.com>
Auto-Submit: Asami Doi <asamidoi@chromium.org>
Commit-Queue: Asami Doi <asamidoi@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1368172}