panic: `Option::unwrap()` on a `None` value

This is a fuzzer-generated bug, please feel free to close and/or let me know if it's not helpful!

rustfmt 1.5.2-nightly (2eaeb1e 2023-04-05)

enum En4<'x1, 'x2, T: Tr1<As1:  >> {
    V0,
    V1,
}

enum _En5<'x1, 'x2, T: Tr1<As1:  >> {
    _V0,
    _V1,
}

enum En6
where
    T: Tr1<En2<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S<S>>>>>>>>>>>>>>>>>>>>>>>>,
{
    V0,
    V1,
    V2,
    V3,
}

enum _En7 
where
    T: ,
{
    V0,
    V1,
}

fn _make_en7()
where
    T: ,
{
    
}

enum EnSelf<T> where Self: Tr1<As1: > {
    V0(T),
    V1,
    V2,
}

impl  EnSelf {  }

fn main() {
    if  ::Outest("") = wrap_en1_1::<_> {  };
    ;
    ;
}

thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', src/tools/rustfmt/src/items.rs:439:10
stack backtrace:
   0: rust_begin_unwind
             at /rustc/2eaeb1eee1b21772de8b935236d16ff8e03fdcf5/library/std/src/panicking.rs:577:5
   1: core::panicking::panic_fmt
             at /rustc/2eaeb1eee1b21772de8b935236d16ff8e03fdcf5/library/core/src/panicking.rs:67:14
   2: core::panicking::panic
             at /rustc/2eaeb1eee1b21772de8b935236d16ff8e03fdcf5/library/core/src/panicking.rs:117:5
   3: <rustfmt_nightly::visitor::FmtVisitor>::visit_item
   4: <rustfmt_nightly::visitor::FmtVisitor>::visit_items_with_reordering
   5: <rustfmt_nightly::visitor::FmtVisitor>::walk_mod_items
   6: <rustfmt_nightly::visitor::FmtVisitor>::format_separate_mod
   7: rustfmt_nightly::formatting::format_project::<rustfmt_nightly::Session<std::io::stdio::Stdout>>
   8: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::with::<<rustfmt_nightly::Session<std::io::stdio::Stdout>>::format_input_inner::{closure#0}, core::result::Result<rustfmt_nightly::FormatReport, rustfmt_nightly::ErrorKind>>
   9: <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_span::create_session_if_not_set_then<core::result::Result<rustfmt_nightly::FormatReport, rustfmt_nightly::ErrorKind>, <rustfmt_nightly::Session<std::io::stdio::Stdout>>::format_input_inner::{closure#0}>::{closure#0}, core::result::Result<rustfmt_nightly::FormatReport, rustfmt_nightly::ErrorKind>>
  10: <rustfmt_nightly::Session<std::io::stdio::Stdout>>::format
  11: rustfmt::format_and_emit_report::<std::io::stdio::Stdout>
  12: <rustfmt_nightly::Session<std::io::stdio::Stdout>>::override_config::<rustfmt::format::{closure#0}, ()>
  13: rustfmt::execute
  14: rustfmt::main
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.