panic: Incrementing non-positive ref count

goroutine 1376836 [running]:
gvisor.googlesource.com/gvisor/pkg/refs.(*AtomicRefCount).IncRef(0xc4205b1b00)
	pkg/refs/refcounter.go:211 +0x79
gvisor.googlesource.com/gvisor/pkg/sentry/mm.(*MemoryManager).Fork(0xc420984c80, 0x10f3540, 0xc4219e4900, 0x0, 0x0, 0x0)
	pkg/sentry/mm/lifecycle.go:90 +0x892
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*TaskContext).Fork(0xc4219e5030, 0x10f3540, 0xc4219e4900, 0x0, 0x0, 0x0, 0x0)
	pkg/sentry/kernel/task_context.go:89 +0x2e4
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).Clone(0xc4219e4900, 0xc4212f98f8, 0x0, 0x0, 0x0, 0x0)
	pkg/sentry/kernel/task_clone.go:203 +0x2f9
gvisor.googlesource.com/gvisor/pkg/sentry/syscalls/linux.clone(0xc4219e4900, 0x1000000, 0x200007c0, 0x200008c0, 0x20000900, 0x20000940, 0x42f108, 0xc42004aa00, 0x46154c, 0x876bb8)
	pkg/sentry/syscalls/linux/sys_thread.go:157 +0x22f
gvisor.googlesource.com/gvisor/pkg/sentry/syscalls/linux.Clone(0xc4219e4900, 0x1000000, 0x200007c0, 0x200008c0, 0x20000900, 0x20000940, 0x0, 0x47b89e, 0xc4212f9a88, 0x42f404, ...)
	pkg/sentry/syscalls/linux/sys_thread.go:171 +0x81
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0xc4219e4900, 0x38, 0x1000000, 0x200007c0, 0x200008c0, 0x20000900, 0x20000940, 0x0, 0x0, 0x0, ...)
	pkg/sentry/kernel/task_syscall.go:162 +0x14f
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0xc4219e4900, 0x38, 0x1000000, 0x200007c0, 0x200008c0, 0x20000900, 0x20000940, 0x0, 0x1000000, 0x200007c0)
	pkg/sentry/kernel/task_syscall.go:278 +0x7e
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0xc4219e4900, 0x38, 0x1000000, 0x200007c0, 0x200008c0, 0x20000900, 0x20000940, 0x0, 0xc42048d960, 0xc4212f9c68)
	pkg/sentry/kernel/task_syscall.go:241 +0xc4
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0xc4219e4900, 0x2, 0xc420a8a120)
	pkg/sentry/kernel/task_syscall.go:216 +0x19d
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*runApp).execute(0x0, 0xc4219e4900, 0x10e4580, 0x0)
	pkg/sentry/kernel/task_run.go:217 +0x1502
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).run(0xc4219e4900, 0x2b71)
	pkg/sentry/kernel/task_run.go:95 +0x265
created by gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).Start
	pkg/sentry/kernel/task_start.go:258 +0x194