fix: null pointer in call participants list [WPB-15783]

[Garzas]

WPB-15783 [Android] Unexpected drop from call in MLS group

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What's new in this PR?

Issues

• Fixed IndexOutOfBoundsException in VerticalCallingPager that occurred when removing the first participant (self user) in Picture-in-Picture (PiP) mode.
• Prevented crashes when accessing participantsChunkedList due to inconsistent page count calculations.

Causes (Optional)

• When PiP mode was enabled and there was more than one participant, the first participant was removed using subList(1, participants.size). However, pagerState.pageCount was calculated before this modification, leading to a mismatch in page count.
• The rememberPagerState relied on participants.size, which didn't reflect the adjusted participant list after subList(), sometimes leading to pageIndex being out of range.
• The LaunchedEffect block was trying to access participantsChunkedList[pagerState.currentPage] without verifying if pageIndex was within bounds.

Solutions

• Moved newParticipants calculation outside of VerticalPager, ensuring it is computed before pagerState.pageCount is determined.
• Updated pagerState to correctly reflect the actual number of pages by using participantsChunkedList.size instead of the original participants.size.
• Added safe access with getOrNull(pageIndex) when retrieving elements from participantsChunkedList to prevent IndexOutOfBoundsException.
• Ensured LaunchedEffect only attempts to request video streams when the current page index is valid.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

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