panic: Incrementing non-positive ref count

goroutine 3749461 [running]:
gvisor.googlesource.com/gvisor/pkg/refs.(*AtomicRefCount).IncRef(0xc4b28ae600)
	pkg/refs/refcounter.go:215 +0x5a
gvisor.googlesource.com/gvisor/pkg/sentry/mm.(*MemoryManager).Fork(0xc4b0c36c80, 0xc610e0, 0xc4afcbe400, 0x0, 0x0, 0x0)
	pkg/sentry/mm/lifecycle.go:90 +0x471
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*TaskContext).Fork(0xc4afcbeb30, 0xc610e0, 0xc4afcbe400, 0xc4afcbe400, 0x3, 0xc4a4f4da06, 0x3)
	pkg/sentry/kernel/task_context.go:91 +0x16d
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).Clone(0xc4afcbe400, 0xc4a4f4dab8, 0x0, 0x0, 0x0, 0x0)
	pkg/sentry/kernel/task_clone.go:203 +0x1b1
gvisor.googlesource.com/gvisor/pkg/sentry/syscalls/linux.clone(0xc4afcbe400, 0x0, 0x20000640, 0x20001640, 0x20001680, 0x200016c0, 0x8ef9, 0xc4a4f4db88, 0x40000002, 0x0)
	pkg/sentry/syscalls/linux/sys_thread.go:157 +0x21b
gvisor.googlesource.com/gvisor/pkg/sentry/syscalls/linux.Clone(0xc4afcbe400, 0x0, 0x20000640, 0x20001640, 0x20001680, 0x200016c0, 0x0, 0x202, 0xc4a4f4dc10, 0x428854, ...)
	pkg/sentry/syscalls/linux/sys_thread.go:171 +0x67
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0xc4afcbe400, 0x38, 0x0, 0x20000640, 0x20001640, 0x20001680, 0x200016c0, 0x0, 0x0, 0xba0f20, ...)
	pkg/sentry/kernel/task_syscall.go:162 +0x307
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0xc4afcbe400, 0x38, 0x0, 0x20000640, 0x20001640, 0x20001680, 0x200016c0, 0x0, 0x200016c0, 0x0)
	pkg/sentry/kernel/task_syscall.go:280 +0x62
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0xc4afcbe400, 0x38, 0x0, 0x20000640, 0x20001640, 0x20001680, 0x200016c0, 0x0, 0xc53ee0, 0x0)
	pkg/sentry/kernel/task_syscall.go:241 +0x91
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0xc4afcbe400, 0x2, 0xc42030d7a0)
	pkg/sentry/kernel/task_syscall.go:216 +0x142
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*runApp).execute(0x0, 0xc4afcbe400, 0xc53ee0, 0x0)
	pkg/sentry/kernel/task_run.go:219 +0xe56
gvisor.googlesource.com/gvisor/pkg/sentry/kernel.(*Task).run(0xc4afcbe400, 0x5fab)
	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