fix(ios): large title transition accounts for back button with no text

[liamdebeasi]

Issue number: resolves #28751

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What is the current behavior?

The large title transition does not account for back buttons with no text value. We assume that the .button-text element is always defined, but that is not the case when text="" on the back button. As a result, devs were getting errors because we tried to get the bounding box of a undefined.

What is the new behavior?

• Revised the large title logic to only grab values from the back button text if the back button text element is actually defined

There should be no behavior change when the back button text element is defined.

Does this introduce a breaking change?

• Yes
• No

Other information

Dev Build: 7.8.5-dev.11713282122.18cabf98

⚠️ Reviewers: Please test this in the sample application on the linked issue. Please be sure to test the following conditions:

1. When the back button text is defined
2. When the back button text is not defined
3. With the default font scale
4. With a larger font scale

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[sean-perkins]

Observing a shift to both the button and the large title when popping the view. Doesn't happen consistently, but seems to be related to adjusting the text size.

Could be a Safari quirk if you aren't able to reliable reproduce. I can get Safari's header UI to break/run into the content, so there could be more factors here.

RPReplay_Final1713460282.MP4

[liamdebeasi]

If you set text=" " on the BackButton (note the space) based off main, does the issue reproduce?

[thetaPC]

LGTM, worked on the original repo and on a simulator

[sean-perkins]

Tested against the latest changes of v7 with text=" " and was unable to reproduce the video I attached earlier.

Tested again with the dev-build and was only able to get in that state once with changing the dynamic font scaling, but was unable to reproduce with the same steps consistently. Navigated 40+ times without the issue presenting itself with a consistent dynamic font scale.

I think these changes are good to merge. There is a rendering quirk in Safari's UI with changing the dynamic font scale with the address bar at the top of the screen that is having other impact (at random, but not very common). If we get issue reports we can do a deeper evaluation of what is going on there.