When mounting volumes: `panic: runtime error: index out of range`

Description
A panic is displayed when running a docker image with a volume mounted to some source paths on the host machine.

Steps to reproduce the issue:

1. Pull any docker image
2. Run docker image with a volume binding where the source path is an unsigned integer less than 10

For example:

docker pull ubuntu:18.04
docker run -v 0:/data ubuntu:18.04

Describe the results you received:

• A golang panic is raised.
• This occurs regardless of if a file exists with the name.
• This also occurs if the filename is quoted docker run -v "0":/data ubuntu:18.04
• An integer equal or greater than 10 works as expected.
• A negative integer raises a descriptive error

panic: runtime error: index out of range

goroutine 1 [running]:
github.com/docker/cli/cli/compose/loader.isFilePath(0xc000224498, 0x1, 0x5572cd090710)
        /go/src/github.com/docker/cli/cli/compose/loader/volume.go:121 +0x11d
github.com/docker/cli/cli/compose/loader.populateType(0xc0002692a8)
        /go/src/github.com/docker/cli/cli/compose/loader/volume.go:102 +0x76
github.com/docker/cli/cli/compose/loader.ParseVolume(0x7ffc63a8e696, 0x7, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
        /go/src/github.com/docker/cli/cli/compose/loader/volume.go:44 +0x3f8
github.com/docker/cli/cli/command/container.parse(0xc0004b0500, 0xc000232580, 0xc000224040, 0x5, 0x0, 0x0, 0xc0004ba380)
        /go/src/github.com/docker/cli/cli/command/container/opts.go:344 +0x291
github.com/docker/cli/cli/command/container.runRun(0x5572cbeb6220, 0xc000258000, 0xc0004b0500, 0xc00005fec0, 0xc000232580, 0x5572cb0d0f62, 0x5572ca3cee70)
        /go/src/github.com/docker/cli/cli/command/container/run.go:81 +0x4c0
github.com/docker/cli/cli/command/container.NewRunCommand.func1(0xc0002d4a00, 0xc000028180, 0x1, 0x3, 0x0, 0x0)
        /go/src/github.com/docker/cli/cli/command/container/run.go:47 +0xff
github.com/docker/cli/vendor/github.com/spf13/cobra.(*Command).execute(0xc0002d4a00, 0xc00051d990, 0x3, 0x3, 0xc0002d4a00, 0xc00051d990)
        /go/src/github.com/docker/cli/vendor/github.com/spf13/cobra/command.go:762 +0x467
github.com/docker/cli/vendor/github.com/spf13/cobra.(*Command).ExecuteC(0xc00046b180, 0xc00051d980, 0x4, 0x4)
        /go/src/github.com/docker/cli/vendor/github.com/spf13/cobra/command.go:852 +0x2ee
github.com/docker/cli/vendor/github.com/spf13/cobra.(*Command).Execute(...)
        /go/src/github.com/docker/cli/vendor/github.com/spf13/cobra/command.go:800
main.runDocker(0xc000258000, 0x5572cbe1e8c0, 0xc000010020)
        /go/src/github.com/docker/cli/cmd/docker/docker.go:281 +0x1d5
main.main()
        /go/src/github.com/docker/cli/cmd/docker/docker.go:292 +0xf3

Describe the results you expected:
I expect either the command to succeed if the file exists or an error saying the file does not exist.

Additional information you deem important (e.g. issue happens only occasionally):

Output of docker version:

Client: Docker Engine - Community
 Version:           19.03.4
 API version:       1.40
 Go version:        go1.12.10
 Git commit:        9013bf583a
 Built:             Fri Oct 18 15:54:09 2019
 OS/Arch:           linux/amd64
 Experimental:      false

Server: Docker Engine - Community
 Engine:
  Version:          19.03.4
  API version:      1.40 (minimum version 1.12)
  Go version:       go1.12.10
  Git commit:       9013bf583a
  Built:            Fri Oct 18 15:52:40 2019
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.2.10
  GitCommit:        b34a5c8af56e510852c35414db4c1f4fa6172339
 runc:
  Version:          1.0.0-rc8+dev
  GitCommit:        3e425f80a8c931f88e6d94a8c831b9d5aa481657
 docker-init:
  Version:          0.18.0
  GitCommit:        fec3683

Output of docker info:

Client:
 Debug Mode: false

Server:
 Containers: 37
  Running: 0
  Paused: 0
  Stopped: 37
 Images: 130
 Server Version: 19.03.4
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Native Overlay Diff: true
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: b34a5c8af56e510852c35414db4c1f4fa6172339
 runc version: 3e425f80a8c931f88e6d94a8c831b9d5aa481657
 init version: fec3683
 Security Options:
  apparmor
  seccomp
   Profile: default
 Kernel Version: 4.15.0-66-generic
 Operating System: Ubuntu 18.04.3 LTS
 OSType: linux
 Architecture: x86_64
 CPUs: 8
 Total Memory: 15.41GiB
 Name: consistency
 ID: UK7B:2DQI:KBNU:I5SR:S3AM:ATYF:MNZD:QRD6:DO53:U6SY:67JG:KJGG
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

WARNING: No swap limit support

Additional environment details (AWS, VirtualBox, physical, etc.):

Thinkpad X1 Carbon 7th Generation

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04.3 LTS
Release:        18.04
Codename:       bionic

Start in cli/compose/loader/volume.go, following the stack trace through ParseVolume, populateType, and isFilePath. Reproduce the issue with docker run -v 0:/data ubuntu:18.04 and compare it with a source path of 10 or greater. Done means the command no longer panics and either succeeds for an existing path or reports that the path does not exist.