Not quoting fields in config.toml causes SIGSEGV

[CodingCellist]

What version of Hugo are you using (hugo version)?

$ hugo version
hugo v0.85.0+extended linux/amd64 BuildDate=unknown

OS: Linux 5.12.17

Does this issue reproduce with the latest release?

AFAICT, v0.85.0 is the latest release, so yes.

Issue

Create a new hugo module with hugo mod init foo and set up the config.toml as follows:

[module]
  [[module.imports]]
    path = github.com/bar/baz

Then run hugo mod get.

Expected behaviour

Hugo reports a parse error because github.com/bar/baz needs to be quoted.

Observed behaviour

Hugo crashes with a runtime error caused by SIGSEGV

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x4e010785b1e]

goroutine 1 [running]:
github.com/gohugoio/hugo/commands.(*commandeer).loadConfig(0xc000529180, 0xc000520000, 0x4e0111e5238, 0xc000715de0)
	github.com/gohugoio/hugo/commands/commandeer.go:319 +0x45e
github.com/gohugoio/hugo/commands.newCommandeer(0x68c486eb0000, 0xc000528fc0, 0x4e0111e25d8, 0xc0007924b0, 0x0, 0x0, 0x0, 0x0, 0x98, 0x620004e01112aee0, ...)
	github.com/gohugoio/hugo/commands/commandeer.go:182 +0x267
github.com/gohugoio/hugo/commands.initializeConfig(0x4e010940000, 0xc000528fc0, 0x4e0111e25d8, 0xc0007924b0, 0x0, 0x4e00f44bd36, 0x4e010952b78, 0x5)
	github.com/gohugoio/hugo/commands/hugo.go:123 +0x78
github.com/gohugoio/hugo/commands.(*modCmd).initConfig(0xc0007924b0, 0x0, 0x4e01094e90a, 0x4, 0xc0005586e0)
	github.com/gohugoio/hugo/commands/mod.go:287 +0x65
github.com/gohugoio/hugo/commands.(*modCmd).withModsClient(0xc0007924b0, 0xc00087fc00, 0xc00087fc98, 0xc00056aa00, 0xc00087fce8)
	github.com/gohugoio/hugo/commands/mod.go:269 +0x3a
github.com/gohugoio/hugo/commands.(*commandsBuilder).newModCmd.func1(0xc0001e1680, 0x4e011de05a0, 0x0, 0x0, 0x0, 0x0)
	github.com/gohugoio/hugo/commands/mod.go:199 +0x245
github.com/spf13/cobra.(*Command).execute(0xc0001e1680, 0x4e011de05a0, 0x0, 0x0, 0xc0001e1680, 0x4e011de05a0)
	github.com/spf13/cobra@v1.1.3/command.go:852 +0x472
github.com/spf13/cobra.(*Command).ExecuteC(0xc0001edb80, 0xc000715c10, 0x5, 0x6)
	github.com/spf13/cobra@v1.1.3/command.go:960 +0x375
github.com/gohugoio/hugo/commands.Execute(0xc00003c0a0, 0x2, 0x2, 0x4e00f2d40e5, 0xc0000a6058, 0x4e0107b29b0, 0x0)
	github.com/gohugoio/hugo/commands/hugo.go:90 +0xc5
main.main()
	github.com/gohugoio/hugo/main.go:23 +0x76