Encrypted file that was modified outside of sops not decryptable, go panic.

I am suddenly not able to decrypt a file anymore. I am not sure what the issue is. Here is the stacktrace:

sops --verbose -d -i spigot2.yml
[PGP]    INFO[0000] Decryption succeeded                          fingerprint=6862BCF4AFF6514F668E7A6059365879AABD9BFE
[SOPS]   INFO[0000] Data key recovered successfully
[SOPS]   DEBU[0000] Decrypting tree
panic: interface conversion: interface {} is int, not string

goroutine 1 [running]:
go.mozilla.org/sops.Tree.Decrypt.func1.1(0xecd640, 0xc0003dc0e0, 0xc0003ce170, 0x1, 0x1, 0x0, 0x415b5f, 0x7f6416e6c500, 0x20300000000000)
        /home/travis/gopath/src/go.mozilla.org/sops/sops.go:415 +0x991
go.mozilla.org/sops.TreeBranch.walkValue(0xc00028d600, 0x7, 0x8, 0xecd640, 0xc000386560, 0xc0003ce170, 0x1, 0x1, 0xc000264438, 0x7f641704cfff, ...)
        /home/travis/gopath/src/go.mozilla.org/sops/sops.go:225 +0x81c
go.mozilla.org/sops.TreeBranch.walkBranch(0xc00028d600, 0x7, 0x8, 0xc00028d600, 0x7, 0x8, 0x1b3cb58, 0x0, 0x0, 0xc000264438, ...)
        /home/travis/gopath/src/go.mozilla.org/sops/sops.go:278 +0x4c2
go.mozilla.org/sops.Tree.Decrypt.func1(0xc00028d600, 0x7, 0x8, 0xc0003ce160, 0x1)
        /home/travis/gopath/src/go.mozilla.org/sops/sops.go:370 +0x195
go.mozilla.org/sops.Tree.Decrypt(0x0, 0xed56d23eb, 0x0, 0xc000386de0, 0xc, 0x0, 0x0, 0x0, 0x0, 0xc0002a4360, ...)
        /home/travis/gopath/src/go.mozilla.org/sops/sops.go:436 +0x27c
go.mozilla.org/sops/cmd/sops/common.DecryptTree(0xc00032bba0, 0xc000368470, 0x1, 0x1, 0x0, 0x12c5480, 0xc00035e570, 0xc000368470, 0x1, 0x1, ...)
        /home/travis/gopath/src/go.mozilla.org/sops/cmd/sops/common/common.go:57 +0x1ed
main.decrypt(0x12c5480, 0xc00035e570, 0x7f64197f8728, 0x1b3cb58, 0x7f64197f8728, 0x1b3cb58, 0xc00013e9c0, 0x36, 0x0, 0x0, ...)
        /home/travis/gopath/src/go.mozilla.org/sops/cmd/sops/decrypt.go:34 +0x1f9
main.main.func6(0xc0000b1080, 0x0, 0x0)
        /home/travis/gopath/src/go.mozilla.org/sops/cmd/sops/main.go:572 +0x2b12
gopkg.in/urfave/cli%2ev1.HandleAction(0xeeb3e0, 0x10f2c78, 0xc0000b1080, 0x0, 0x0)
        /home/travis/gopath/pkg/mod/gopkg.in/urfave/cli.v1@v1.20.0/app.go:490 +0xc8
gopkg.in/urfave/cli%2ev1.(*App).Run(0xc0002eed00, 0xc0000c0000, 0x5, 0x5, 0x0, 0x0)
        /home/travis/gopath/pkg/mod/gopkg.in/urfave/cli.v1@v1.20.0/app.go:264 +0x57c
main.main()
        /home/travis/gopath/src/go.mozilla.org/sops/cmd/sops/main.go:720 +0x2860

This is a yaml file encrypted with pgp.

sops 3.5.0 (latest)
Ubuntu 18.04.3 LTS amd64

Feel free to message me privately if you would like the yaml file and PGP key.

Start in sops.go at Tree.Decrypt around line 415, using the reported panic and the encrypted YAML modified outside SOPS as the reproduction. Trace the decryption path and add a regression test for this input; done means decryption reports an error or succeeds without panicking.