fix(segment-button): protect connectedCallback for when segment-content has not yet been created (#30133)

Issue number: internal

---------

<!-- Please do not submit updates to dependencies unless it fixes an
issue. -->

<!-- Please try to limit your pull request to one type (bugfix, feature,
etc). Submit multiple pull requests if needed. -->

## What is the current behavior?
<!-- Please describe the current behavior that you are modifying. -->
When the `connectedCallback` method is called for a segment-button and
its corresponding segment-content has not been created in that instant,
a console error is thrown and the method returns.

## What is the new behavior?
<!-- Please describe the behavior or changes that are being added by
this PR. -->
- `connectedCallback` will now wait, at most 1 second, for the
corresponding segment-content to be created.
- The new behaviour can be tested in segment-view/basic.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

<!--
  If this introduces a breaking change:
1. Describe the impact and migration path for existing applications
below.
  2. Update the BREAKING.md file with the breaking change.
3. Add "BREAKING CHANGE: [...]" to the commit description when merging.
See
https://github.com/ionic-team/ionic-framework/blob/main/docs/CONTRIBUTING.md#footer
for more information.
-->


## Other information

<!-- Any other information that is important to this PR such as
screenshots of how the component looks before and after the change. -->

core/src/components/segment-view/test/basic/index.html

@@ -123,6 +123,8 @@
         <button class="expand" onClick="changeSegmentContent()">Change Segment Content</button>
 
         <button class="expand" onClick="clearSegmentValue()">Clear Segment Value</button>
+
+        <button class="expand" onClick="addSegmentButtonAndContent()">Add New Segment Button & Content</button>
       </ion-content>
 
       <ion-footer>
@@ -158,6 +160,34 @@
             segment.value = undefined;
           });
         }
+
+        async function addSegmentButtonAndContent() {
+          const segment = document.querySelector('ion-segment');
+          const segmentView = document.querySelector('ion-segment-view');
+
+          const newButton = document.createElement('ion-segment-button');
+          const newId = `new-${Date.now()}`;
+          newButton.setAttribute('content-id', newId);
+          newButton.setAttribute('value', newId);
+          newButton.innerHTML = '<ion-label>New Button</ion-label>';
+
+          segment.appendChild(newButton);
+
+          setTimeout(() => {
+            // Timeout to test waitForSegmentContent() in segment-button
+            const newContent = document.createElement('ion-segment-content');
+            newContent.setAttribute('id', newId);
+            newContent.innerHTML = 'New Content';
+
+            segmentView.appendChild(newContent);
+
+            // Necessary timeout to ensure the value is set after the content is added.
+            // Otherwise, the transition is unsuccessful and the content is not shown.
+            setTimeout(() => {
+              segment.setAttribute('value', newId);
+            }, 200);
+          }, 200);
+        }
       </script>
     </ion-app>
   </body>