Compile error with GS project

[chrissimpkins]

@MariannaPaszkowska identified the following compiler error today

fontc 484450e
rustc 1.72.1 (d5c2e9c34 2023-09-13)
macOS Monterey v12.6.7
GS main branch commit

cargo run --package fontc -- --source /Users/…/GitHub/googlesans/source/GoogleSans/GoogleSans.designspace 
    Finished dev [unoptimized + debuginfo] target(s) in 1.70s
     Running `target/debug/fontc --source /Users/…./GitHub/googlesans/source/GoogleSans/GoogleSans.designspace`
thread '<unnamed>' panicked at 'assertion failed: `(left == right)`
  left: `Space(0)`,
 right: `Space(1)`', /Users/…/.cargo/registry/src/index.crates.io-6f17d22bba15001f/write-fonts-0.18.0/src/graph.rs:797:13
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
[2023-11-09T13:21:38.379561Z main fontc::workload ERROR] Be(Features) failed Job panicked: 'assertion failed: `(left == right)`
  left: `Space(0)`,
 right: `Space(1)`'
At least one work item failed

[rsheeter]

Ty for the detailed report; I believe this is fixed by #560