fatal error: sync: unlock of unlocked mutex

[selden]

Tweego -w died while I was messing around with studying the effects of Greyelf's recent suggestions for removing margins in SugarCube. See https://intfiction.org/t/left-margin-padding-wont-go-away/44981

I'm using
Tweego v2.1.1+81d1d71
SugarCube v2.31.1

Specifically, I added this code to Story Javascript:

div#passages {
    max-width: none;
}
#story {
	margin-left: 0;
	margin-right: 0;
}

and then deleted the line

	margin-left: 0;

since it hid the left side of passages behind the UI bar.

Here's the terminal output:

$ ~/tw.sh Evaluation_v0.1
+ tweego -w Evaluation_v0.1 common_source -o Evaluation_v0.1.html

Watch mode started.  Press CTRL+C to stop.

Recursively watched paths: 2
  Evaluation_v0.1
  common_source

BUILDING: Evaluation_v0.1.html
CREATE: common_source\.#gui-common.tw
BUILDING: Evaluation_v0.1.html
WRITE: common_source\gui-common.tw
REMOVE: common_source\.#gui-common.tw
BUILDING: Evaluation_v0.1.html
fatal error: sync: unlock of unlocked mutex

goroutine 1 [running]:
runtime.throw(0x5dcf2f, 0x1e)
        c:/devel/go/src/runtime/panic.go:774 +0x79 fp=0xc00007d9b0 sp=0xc00007d980 pc=0x42ee89
sync.throw(0x5dcf2f, 0x1e)
        c:/devel/go/src/runtime/panic.go:760 +0x3c fp=0xc00007d9d0 sp=0xc00007d9b0 pc=0x42edfc
sync.(*Mutex).unlockSlow(0xc00000a2b0, 0xffffffff)
        c:/devel/go/src/sync/mutex.go:196 +0xdd fp=0xc00007d9f8 sp=0xc00007d9d0 pc=0x474bed
sync.(*Mutex).Unlock(0xc00000a2b0)
        c:/devel/go/src/sync/mutex.go:190 +0x4f fp=0xc00007da18 sp=0xc00007d9f8 pc=0x474aff
runtime.call32(0x0, 0x5f9ce0, 0xc00007db78, 0x800000008)
        c:/devel/go/src/runtime/asm_amd64.s:539 +0x42 fp=0xc00007da48 sp=0xc00007da18 pc=0x456e22
panic(0x5a0760, 0xc0000670e0)
        c:/devel/go/src/runtime/panic.go:679 +0x1c0 fp=0xc00007dad8 sp=0xc00007da48 pc=0x42e9b0
runtime.panicdottypeE(...)
        c:/devel/go/src/runtime/iface.go:255
runtime.panicdottypeI(0x623f80, 0x5a2a60, 0x5a1ac0)
        c:/devel/go/src/runtime/iface.go:265 +0xfb fp=0xc00007db00 sp=0xc00007dad8 pc=0x4099db
github.com/radovskyb/watcher.(*Watcher).retrieveFileList(0xc00008a080, 0x0)
        c:/devel/local/go/pkg/mod/github.com/radovskyb/watcher@v1.0.7/watcher.go:500 +0x719 fp=0xc00007dc90 sp=0xc00007db00 pc=0x51a
089
github.com/radovskyb/watcher.(*Watcher).Start(0xc00008a080, 0x3b9aca00, 0x0, 0x1)
        c:/devel/local/go/pkg/mod/github.com/radovskyb/watcher@v1.0.7/watcher.go:563 +0x396 fp=0xc00007de30 sp=0xc00007dc90 pc=0x51a
436
main.watchFilesystem(0xc0000049c0, 0x2, 0x2, 0xc0000105a0, 0x14, 0xc000004a20)
        c:/devel/local/src/tweego/filesystem.go:177 +0x354 fp=0xc00007dec0 sp=0xc00007de30 pc=0x55bd34
main.main()
        c:/devel/local/src/tweego/tweego.go:30 +0x191 fp=0xc00007df60 sp=0xc00007dec0 pc=0x56e8a1
runtime.main()
        c:/devel/go/src/runtime/proc.go:203 +0x21e fp=0xc00007dfe0 sp=0xc00007df60 pc=0x43086e
runtime.goexit()
        c:/devel/go/src/runtime/asm_amd64.s:1357 +0x1 fp=0xc00007dfe8 sp=0xc00007dfe0 pc=0x458ba1

goroutine 83 [select]:
main.watchFilesystem.func1(0x1dcd6500, 0xc000004a20, 0xc00008a080)
        c:/devel/local/src/tweego/filesystem.go:118 +0x14a
created by main.watchFilesystem
        c:/devel/local/src/tweego/filesystem.go:114 +0x105