Json Fail: `tileRectsIds`

[Cammin]

I found a json deserialization failure when making rules: the tileRectsIds of a rule definition can have a null value in it.

The json deserializer expects an int[][] for the c# schema, but it's possible to save the project with a null value in it, and so it errors out.

It's possible that this can happen because of this "error" visual after I deleted some parts of my project: