Encode crashes on `null` object values about ts-proto

[stephenh]

@gabrielOttopia can you include the snippet of code from encode that stack traces?

Are you using the useNullAsOptional flag introduced in #1017 ? Historically we've not supported null, so unless you're using useNullAsOptional that behavior is probably expected.

[gabrielOttopia]

@stephenh I tried that flag and got this error:

`src/autogenerated/X/X_management.ts:241:96 - error TS2345: Argument of type '{ clientId?: { id?: string | undefined; } | null | undefined; stationId?: { id?: { id?: string | undefined; } | null | undefined; address?: { ipv4?: number | null | undefined; ipv6?: Uint8Array | null | undefined; } | null | undefined; } | null | undefined; }' is not assignable to parameter of type '{ clientId?: { id?: string | undefined; } | null | undefined; stationId?: { id?: { id?: string | undefined; } | null | undefined; address?: { ipv4?: number | null | undefined; ipv6?: Uint8Array | null | undefined; } | null | undefined; } | null | undefined; } & { ...; } & {}'.
  Type '{ clientId?: { id?: string | undefined; } | null | undefined; stationId?: { id?: { id?: string | undefined; } | null | undefined; address?: { ipv4?: number | null | undefined; ipv6?: Uint8Array | null | undefined; } | null | undefined; } | null | undefined; }' is not assignable to type '{ clientId?: ({ id?: string | undefined; } & { id?: string | undefined; } & {}) | undefined; stationId?: ({ id?: { id?: string | undefined; } | null | undefined; address?: { ipv4?: number | null | undefined; ipv6?: Uint8Array | ... 1 more ... | undefined; } | null | undefined; } & { ...; } & {}) | undefined; }'.
    Types of property 'clientId' are incompatible.
      Type '{ id?: string | undefined; } | null | undefined' is not assignable to type '({ id?: string | undefined; } & { id?: string | undefined; } & {}) | undefined'.
        Type 'null' is not assignable to type '({ id?: string | undefined; } & { id?: string | undefined; } & {}) | undefined'.

241     message.connectedClients = object.connectedClients?.map((e) => ConnectedClient.fromPartial(e)) || [];
`

`      Type '{ id?: string | undefined; } | null | undefined' is not assignable to type '({ id?: string | undefined; } & { id?: string | undefined; } & {}) | undefined'.
        Type 'null' is not assignable to type '({ id?: string | undefined; } & { id?: string | undefined; } & {}) | undefined'.ts(2345)
`

the error snipped i get probably wont be too helpful