'rustup target list' panics

[jdeeny]

When I try to look at a list of targets with 'rustup target list', I get a panic:

$ RUST_BACKTRACE=1 rustup target list
thread '<main>' panicked at 'extension should have target toolchain', ../src/libcore/option.rs:699
stack backtrace:
   1:     0x55dd5b444a80 - std::sys::backtrace::tracing::imp::write::h9fb600083204ae7f
   2:     0x55dd5b44cd1b - std::panicking::default_hook::_$u7b$$u7b$closure$u7d$$u7d$::hca543c34f11229ac
   3:     0x55dd5b44c9a3 - std::panicking::default_hook::hc2c969e7453d080c
   4:     0x55dd5b430d3f - std::sys_common::unwind::begin_unwind_inner::h30e12d15ce2b2e25
   5:     0x55dd5b4326c8 - std::sys_common::unwind::begin_unwind_fmt::hb2de8a9968d38523
   6:     0x55dd5b443e41 - rust_begin_unwind
   7:     0x55dd5b4831bf - core::panicking::panic_fmt::h257ceb0aa351d801
   8:     0x55dd5b48a474 - core::option::expect_failed::h2d57a5644f345e0b
   9:     0x55dd5b0e5f67 - rustup::toolchain::Toolchain::list_components::h6f5e5af7ff496961
  10:     0x55dd5b000ba8 - rustup_init::rustup_mode::main::h904c4ed7acbad99d
  11:     0x55dd5aff636e - rustup_init::run_multirust::h70cbf6663515e18b
  12:     0x55dd5aff54e1 - rustup_init::main::h81d74e5ca7cf36c2
  13:     0x55dd5b44c5e4 - std::sys_common::unwind::try::try_fn::h04c0c89e4add6cc4
  14:     0x55dd5b443dcb - __rust_try
  15:     0x55dd5b44c02b - std::rt::lang_start::h61f4934e780b4dfc
  16:     0x7f0cf27d9730 - __libc_start_main
  17:     0x55dd5aff53d4 - <unknown>

[Diggsey]

Duplicate of #664 although good to know it affects target list too.