"attempt to subtract with overflow" printing empty object

Steps to reproduce:
1. `cargo install wrangler --version 1.19.5`
2. `cargo generate --git https://github.com/cloudflare/websocket-template --name websocket`
3. `cd websocket`
4. Apply this diff:
```diff
diff --git a/websocket/index.js b/websocket/index.js
index 0221c8f..baafb4e 100644
--- a/websocket/index.js
+++ b/websocket/index.js
@@ -26,6 +26,7 @@ async function handleSession(websocket) {

const websocketHandler = async request => {
const upgradeHeader = request.headers.get("Upgrade")
+ console.log(request.headers);
if (upgradeHeader !== "websocket") {
return new Response("Expected websocket", { status: 400 })
}
diff --git a/websocket/template.js b/websocket/template.js
index 9ed9b93..c34fb92 100644
--- a/websocket/template.js
+++ b/websocket/template.js
@@ -57,7 +57,7 @@ const template = `
}

const url = new URL(window.location)
- url.protocol = "wss"
+ url.protocol = "ws"
url.pathname = "/ws"
websocket(url)

```
5. Navigate to http://127.0.0.1:8787/.

`chrome_devtools_rs` will panic:

```
2: core::panicking::panic
at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/panicking.rs:50:5
3: ::fmt
at /home/jnelson/.local/lib/cargo/registry/src/github.com-1ecc6299db9ec823/chrome-devtools-rs-0.0.0-alpha.3/src/domain/runtime/type/remote_object/type/object/object_preview/mod.rs:89:38
4: ::to_string
at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/alloc/src/string.rs:2382:9
5: chrome_devtools::domain::runtime::type::remote_object::RemoteObject::display_object
at /home/jnelson/.local/lib/cargo/registry/src/github.com-1ecc6299db9ec823/chrome-devtools-rs-0.0.0-alpha.3/src/domain/runtime/type/remote_object/mod.rs:54:13
6: ::fmt
at /home/jnelson/.local/lib/cargo/registry/src/github.com-1ecc6299db9ec823/chrome-devtools-rs-0.0.0-alpha.3/src/domain/runtime/type/remote_object/mod.rs:102:29
7: <&T as core::fmt::Display>::fmt
at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/fmt/mod.rs:2031:62
8: core::fmt::write
at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/fmt/mod.rs:1110:17
9: core::fmt::Formatter::write_fmt
at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/fmt/mod.rs:1556:9
10: ::fmt
at /home/jnelson/.local/lib/cargo/registry/src/github.com-1ecc6299db9ec823/chrome-devtools-rs-0.0.0-alpha.3/src/domain/runtime/event/console_api_called.rs:22:13
11: <&T as core::fmt::Display>::fmt
at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/fmt/mod.rs:2031:62
12: core::fmt::write
at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/fmt/mod.rs:1110:17
13: core::fmt::Formatter::write_fmt
at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/fmt/mod.rs:1556:9
14: ::fmt
at /home/jnelson/.local/lib/cargo/registry/src/github.com-1ecc6299db9ec823/chrome-devtools-rs-0.0.0-alpha.3/src/domain/runtime/event/mod.rs:39:47
15: ::to_string
at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/alloc/src/string.rs:2382:9
16: wrangler::commands::dev::socket::print_ws_messages::{{closure}}
at /home/jnelson/src/wrangler/src/commands/dev/socket.rs:400:44
17: as core::future::future::Future>::poll
at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/future/mod.rs:80:19
18: as core::future::future::Future>::poll
at /home/jnelson/.local/lib/cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.13.0/src/future/maybe_done.rs:68:48
19: wrangler::commands::dev::socket::listen::{{closure}}::{{closure}}
at /home/jnelson/.local/lib/cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.13.0/src/macros/try_join.rs:132:20
20: as core::future::future::Future>::poll
at /home/jnelson/.local/lib/cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.13.0/src/future/poll_fn.rs:38:9
21: wrangler::commands::dev::socket::listen::{{closure}}
at /home/jnelson/src/wrangler/src/commands/dev/socket.rs:132:16
```