panic: Incrementing non-positive ref count

goroutine 8197861 [running]:
gvisor.googlesource.com/gvisor/pkg/refs.(*AtomicRefCount).IncRef(0xc423000900)
	pkg/refs/refcounter.go:215 +0x5a
gvisor.googlesource.com/gvisor/pkg/sentry/mm.(*MemoryManager).Fork(0xc420887200, 0xc7e8a0, 0xc4232b0900, 0x0, 0x0, 0x0)
	pkg/sentry/mm/lifecycle.go:90 +0x471
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*TaskContext).Fork(0xc4232b1030, 0xc7e8a0, 0xc4232b0900, 0x0, 0xc4208cd910, 0x713df5, 0xc420887200)
	pkg/sentry/kernel/task_context.go:89 +0x16d
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).Clone(0xc4232b0900, 0xc4208cdac8, 0x0, 0x0, 0x0, 0x0)
	pkg/sentry/kernel/task_clone.go:203 +0x1b1
gvisor.googlesource.com/gvisor/pkg/sentry/syscalls/linux.clone(0xc4232b0900, 0x4000, 0x20000380, 0x20000480, 0x200004c0, 0x20000500, 0x40000002, 0x0, 0xf0c8, 0x0)
	pkg/sentry/syscalls/linux/sys_thread.go:157 +0x21b
gvisor.googlesource.com/gvisor/pkg/sentry/syscalls/linux.Clone(0xc4232b0900, 0x4000, 0x20000380, 0x20000480, 0x200004c0, 0x20000500, 0x0, 0x428854, 0xbe69d8, 0xc4208cdc20, ...)
	pkg/sentry/syscalls/linux/sys_thread.go:171 +0x67
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0xc4232b0900, 0x38, 0x4000, 0x20000380, 0x20000480, 0x200004c0, 0x20000500, 0x0, 0xc420296380, 0xbbdd80, ...)
	pkg/sentry/kernel/task_syscall.go:162 +0x307
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0xc4232b0900, 0x38, 0x4000, 0x20000380, 0x20000480, 0x200004c0, 0x20000500, 0x0, 0x20000500, 0x0)
	pkg/sentry/kernel/task_syscall.go:278 +0x62
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0xc4232b0900, 0x38, 0x4000, 0x20000380, 0x20000480, 0x200004c0, 0x20000500, 0x0, 0xc71920, 0xc4208cde18)
	pkg/sentry/kernel/task_syscall.go:241 +0x91
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0xc4232b0900, 0x2, 0xc420950000)
	pkg/sentry/kernel/task_syscall.go:216 +0x10c
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*runApp).execute(0x0, 0xc4232b0900, 0xc71920, 0x0)
	pkg/sentry/kernel/task_run.go:217 +0xe56
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).run(0xc4232b0900, 0x935c)
	pkg/sentry/kernel/task_run.go:95 +0x174
created by gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).Start
	pkg/sentry/kernel/task_start.go:258 +0x100