Global function errors index out of range error

ted@METANDEV:~/Workspace/olang/o-language-learning/samples$ ../../olang/olang c --file encode_udp.ola > compile.
log
0000 OpPop
0001 OpTrue
0002 OpPop
0003 OpConstant 0
0006 OpConstant 1
0009 OpHash 2
0012 OpSetGlobal 0
panic: runtime error: index out of range [-1]

goroutine 1 [running]:
gitlab.com/olanguage/olang/vm.(*VM).pop(...)
        /home/ted/Workspace/olang/olang/vm/vm.go:358
gitlab.com/olanguage/olang/vm.(*VM).Run(0xc000153508)
        /home/ted/Workspace/olang/olang/vm/vm.go:119 +0x1477
gitlab.com/olanguage/olang/repl.FileCompile({0x7ffe83042fad?, 0x1000bf0?}, {0xffa260, 0xc0000940c8}, 0x1?)
        /home/ted/Workspace/olang/olang/repl/repl.go:160 +0x657
main.main.func4(0xc00034eb00)
        /home/ted/Workspace/olang/olang/main.go:216 +0x146
github.com/urfave/cli.HandleAction({0xd6b8a0?, 0xf06518?}, 0x7?)
        /home/ted/go/pkg/mod/github.com/urfave/cli@v1.22.5/app.go:524 +0x50
github.com/urfave/cli.Command.Run({{0xeaa589, 0x7}, {0x0, 0x0}, {0xc0003ed230, 0x1, 0x1}, {0xebf9ce, 0x18}, {0x0, ...}, ...}, ...)
        /home/ted/go/pkg/mod/github.com/urfave/cli@v1.22.5/command.go:173 +0x67c
github.com/urfave/cli.(*App).Run(0xc0003a3c00, {0xc000036200, 0x4, 0x4})
        /home/ted/go/pkg/mod/github.com/urfave/cli@v1.22.5/app.go:277 +0xb1b
main.main()
        /home/ted/Workspace/olang/olang/main.go:490 +0x1334