bake: panic in progress printer

[crazy-max]

https://github.com/docker/buildx/actions/runs/9915811338/job/27397269631?pr=2595#step:6:259

  panic: runtime error: invalid memory address or nil pointer dereference
  [signal SIGSEGV: segmentation violation code=0x1 addr=0x40 pc=0x13d7ba7]
  
  goroutine 10 [running]:
  github.com/docker/buildx/util/progress.(*Printer).Warnings(...)
  	github.com/docker/buildx/util/progress/printer.go:65
  github.com/docker/buildx/commands.runBake.func2()
  	github.com/docker/buildx/commands/bake.go:149 +0x27
  github.com/docker/buildx/util/progress.NewPrinter.func1()
  	github.com/docker/buildx/util/progress/printer.go:129 +0x20a
  created by github.com/docker/buildx/util/progress.NewPrinter in goroutine 1
  	github.com/docker/buildx/util/progress/printer.go:112 +0x2b1

buildx/util/progress/printer.go

Line 65 in 10c9ff9

return dedupWarnings(p.warnings)

[tonistiigi]

Looks like

buildx/commands/bake.go

Line 255 in 10c9ff9

printer = nil

runs before

buildx/commands/bake.go

Line 149 in 10c9ff9

printWarnings(os.Stderr, printer.Warnings(), progressMode)

Note that there is another similar section now in

buildx/commands/bake.go

Line 206 in 10c9ff9

printer = nil

This is a new code in v0.16.0 #2534 . Previously warnings were not printed for Bake.