dedupe doesn't work

On version 6.0.0-rc.20, when I run yarn dedupe it panicks:

RUST_BACKTRACE=1 yarn dedupe

thread 'main' (1840999) panicked at packages/zpm/src/commands/dedupe.rs:208:39:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::panicking::panic
   3: core::option::unwrap_failed
   4: zpm::commands::dedupe::prepare_highest_dedupe::{{closure}}
   5: <core::iter::adapters::filter_map::FilterMap<I,F> as core::iter::traits::iterator::Iterator>::next
   6: zpm::commands::dedupe::Dedupe::execute::{{closure}}
   7: <zpm::commands::YarnCli as clipanion::details::CommandExecutorAsync>::execute::{{closure}}
   8: <S as clipanion::advanced::CliAsync>::run::{{closure}}
   9: zpm::commands::run_default::{{closure}}
  10: <core::pin::Pin<P> as core::future::future::Future>::poll
  11: yarn_bin::main
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Start at packages/zpm/src/commands/dedupe.rs:208 and reproduce the panic with RUST_BACKTRACE=1 yarn dedupe on version 6.0.0-rc.20. Trace the None value from prepare_highest_dedupe and verify that yarn dedupe completes without panicking for the reported case.