Please let’s not get into the “But she won’t be indicted” argument–it doesn’t matter for the sake of this discussion. Just go with the hypothetical please.
Opening night of the convention, Loretta Lynch indicts Hillary for violating national security (or whatever–pick your own indictable offense–doesn’t matter for these purposes).
There’s a factual answer (somewhere) within the Democratic Party rules about what the party is allowed to do. Dems have super-delegates. Could they coalesce behind someone else? Are there rules governing how they decide?
And let’s play the same game with Republicans: Opening night of the convention, Trump gets indicted for insider trading, shady business deals and harassment. What do the Republican Party rules allow? Given that Repubs don’t have super-delegates, what options are allowed under their rules?