Blocking in a deferred function in a promise crashes

Reproduction case:

main.inc.js:

$global.p = new Promise((resolve, reject) => {
    setTimeout(() => {
        resolve("foo");
    }, 300);
});

main.go:

package main

import (
	"fmt"

	"github.com/gopherjs/gopherjs/js"
)

func main() {
	p := js.Global.Get("p")
	p.Call("then", func(r *js.Object) {
		defer func() {
			fmt.Println("deferred")
		}()
	}).Call("catch", func(e *js.Object) {
	})
}

When I execute this code, I get the following output:

deferred
/home/jonhall/src/test/test.js:1737
            r();
            ^

TypeError: r is not a function
    at $runScheduled (/home/jonhall/src/test/test.js:1737:13)
    at $schedule (/home/jonhall/src/test/test.js:1761:9)
    at queueEntry (/home/jonhall/src/test/test.js:1834:9)
    at $send (/home/jonhall/src/test/test.js:1793:9)
    at $b (/home/jonhall/src/test/test.js:15011:9)
    at $b (/home/jonhall/src/test/test.js:14318:9)
    at /home/jonhall/src/test/test.js:68:74
    at FSReqCallback.wrapper [as oncomplete] (node:fs:816:5)

Hypothesis: The rule that blocking code in a callback must be executed in a goroutine should apply to deferred functions within callbacks as well. If I move the fmt.Println call to a goroutine within the deferred function, the error goes away.

Start with the reproduction in main.inc.js and main.go, then inspect the generated test.js stack around $runScheduled, $schedule, queueEntry, and $send. The fix is complete when the deferred function in the promise callback no longer causes a TypeError and the promise chain handles the callback successfully.