lib/ui: fix GridCell.invalid race

This is read/written from different goroutines.

    Write at 0x00c00009c6f0 by goroutine 7:
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Grid).cellInvalidated()
          /home/simon/src/aerc2/lib/ui/grid.go:189 +0x122
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Grid).cellInvalidated-fm()
          /home/simon/src/aerc2/lib/ui/grid.go:178 +0x55
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Invalidatable).DoInvalidate()
          /home/simon/src/aerc2/lib/ui/invalidatable.go:22 +0x85
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Bordered).contentInvalidated-fm()
          /home/simon/src/aerc2/lib/ui/borders.go:39 +0x56
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Invalidatable).DoInvalidate()
          /home/simon/src/aerc2/lib/ui/invalidatable.go:22 +0x85
      git.sr.ht/~sircmpwn/aerc2/widgets.NewDirectoryList.func1()
          /home/simon/src/aerc2/widgets/dirlist.go:81 +0x55
      git.sr.ht/~sircmpwn/aerc2/lib/ui.(*Invalidatable).DoInvalidate()
          /home/simon/src/aerc2/lib/ui/invalidatable.go:22 +0x85
      git.sr.ht/~sircmpwn/aerc2/widgets.(*Spinner).Start.func1()
          /home/simon/src/aerc2/widgets/spinner.go:88 +0x82

    Previous write at 0x00c00009c6f0 by main goroutine:
      [failed to restore the stack]

    Goroutine 7 (running) created at:
      git.sr.ht/~sircmpwn/aerc2/widgets.(*Spinner).Start()
          /home/simon/src/aerc2/widgets/spinner.go:46 +0x98
      git.sr.ht/~sircmpwn/aerc2/widgets.NewDirectoryList()
          /home/simon/src/aerc2/widgets/dirlist.go:37 +0x28b
      git.sr.ht/~sircmpwn/aerc2/widgets.NewAccountView()
          /home/simon/src/aerc2/widgets/account.go:49 +0x5ca
      git.sr.ht/~sircmpwn/aerc2/widgets.NewAerc()
          /home/simon/src/aerc2/widgets/aerc.go:60 +0x807
      main.main()
          /home/simon/src/aerc2/aerc.go:65 +0x33e

0 files changed, 0 insertions, 0 deletions