compose: prevent out of bounds access

Fix the following panic, seen while switching accounts:

runtime error: index out of range [4] with length 4

goroutine 6 [running]:
git.sr.ht/~rjarry/aerc/widgets.(*Composer).Focus(0xc005cfbe30?, 0x40?)
        git.sr.ht/~rjarry/aerc/widgets/compose.go:618 +0x51
git.sr.ht/~rjarry/aerc/widgets.(*Aerc).focus(0xc00034c000, {0x0?, 0x0})
        git.sr.ht/~rjarry/aerc/widgets/aerc.go:568 +0xec
git.sr.ht/~rjarry/aerc/widgets.(*Aerc).BeginExCommand.func2()
        git.sr.ht/~rjarry/aerc/widgets/aerc.go:590 +0x4c
git.sr.ht/~rjarry/aerc/widgets.(*ExLine).Event(0xc009453860, {0xbb6820?, 0xc009baa320?})
        git.sr.ht/~rjarry/aerc/widgets/exline.go:81 +0xbc
git.sr.ht/~rjarry/aerc/widgets.(*Aerc).Event(0xc009ab1950?, {0xbb6820?, 0xc009baa320?})
        git.sr.ht/~rjarry/aerc/widgets/aerc.go:285 +0x470
git.sr.ht/~rjarry/aerc/lib/ui.(*UI).ProcessEvents(0xc000327540)
        git.sr.ht/~rjarry/aerc/lib/ui/ui.go:117 +0x202
created by main.main
        git.sr.ht/~rjarry/aerc/aerc.go:244 +0x94c

Protect Composer.editable and Composer.focus with a mutex.

Reported-by: Bence Ferdinandy <bence@ferdinandy.com>
Signed-off-by: Robin Jarry <robin@jarry.cc>
Acked-by: Moritz Poldrack <moritz@poldrack.dev>

0 files changed, 0 insertions, 0 deletions