UnigramDev/Unigram/develop • 4425c24 • 1 files, +13/-5
Recompute the message index after removing it from the collection (#3352)

InsertMessageInOrder moves a message by removing it and reinserting it at the
index NextIndexOf computed against the collection as it was *before* the
removal, compensating for the single row that goes away. MessageCollection
removes more than one row: RemoveItem also drops the date or topic separator
that the removal orphans, so a message that was the only one of its day takes
its header with it and the collection shrinks by two. If the message is not the
last row -- a sponsored message below it, say -- the adjusted index is then past
the end and Insert throws ArgumentOutOfRangeException.

Reported by crash telemetry on 12.9.1, reached when a locally pending message
completes: PendingMessage_Completed -> InsertMessage -> InsertMessageInOrder.

Ask NextIndexOf again after the removal rather than trusting the pre-removal
index; clamping would have put the message in the wrong place instead. The
force branch had the same defect -- it reinserted at oldIndex, which is out of
bounds once the header ahead of the message is gone -- so both paths now share
one helper.

Not built: the file parses with Roslyn, nothing more.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

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