Unset throws error panic: runtime error: invalid memory address or nil pointer dereference

go_cbq> \unset \\listindex2 $v;

panic: runtime error: invalid memory address or nil pointer dereference

[signal 0xb code=0x1 addr=0x8 pc=0x406e542]

goroutine 16 [running]:

runtime.panic(0x4413800, 0x46ca224)

	/usr/local/go/src/pkg/runtime/panic.c:279 +0xf5

github.com/couchbaselabs/go_cbq/command.PopValue_Helper(0xc208049001, 0xc20800f3e0, 0xc208049027, 0xc, 0x0, 0x0)

	/Users/ketaki/go_cbq/src/github.com/couchbaselabs/go_cbq/command/common.go:322 +0x172

github.com/couchbaselabs/go_cbq/command.(*Unset).ParseCommand(0xc208000b10, 0xc20800fd50, 0x2, 0x2, 0x0, 0x0)

	/Users/ketaki/go_cbq/src/github.com/couchbaselabs/go_cbq/command/unset.go:87 +0x5ef

main.ShellCommandParser(0xc208049020, 0x16, 0x0, 0x0)

	/Users/ketaki/go_cbq/src/github.com/couchbaselabs/go_cbq/shell.go:558 +0x1f1

main.execute_query(0xc208048f00, 0x16, 0x47a9470, 0xc208030008, 0x0, 0x0)

	/Users/ketaki/go_cbq/src/github.com/couchbaselabs/go_cbq/shell.go:415 +0x467

main.HandleInteractiveMode(0x7fff5fbffc8a, 0x6)

	/Users/ketaki/go_cbq/src/github.com/couchbaselabs/go_cbq/interactive.go:134 +0x765

main.main()

	/Users/ketaki/go_cbq/src/github.com/couchbaselabs/go_cbq/shell.go:373 +0xd55

goroutine 19 [finalizer wait]:

runtime.park(0x4019b30, 0x46ead68, 0x46ce109)

	/usr/local/go/src/pkg/runtime/proc.c:1369 +0x89

runtime.parkunlock(0x46ead68, 0x46ce109)

	/usr/local/go/src/pkg/runtime/proc.c:1385 +0x3b

runfinq()

	/usr/local/go/src/pkg/runtime/mgc0.c:2644 +0xcf

runtime.goexit()

	/usr/local/go/src/pkg/runtime/proc.c:1445

goroutine 20 [syscall]:

os/signal.loop()

	/usr/local/go/src/pkg/os/signal/signal_unix.go:21 +0x1e

created by os/signal.init·1

	/usr/local/go/src/pkg/os/signal/signal_unix.go:27 +0x32