[IPC] Various issues with IPC

[marcusbritanicus]

Clear description of the problem
One of the common problems I am facing with IPC is garbage values for various properties. this generally happens because the said property is not set by wayfire. A good example is view-app-id-changed event. The first time this event is emitted, Wayfire has not yet "placed" the view. Therefore, it does not have a wset-index. And the json data contains garbage values like: "wset-index": 18446744073709551615.

This is not an isolated incident. Such behaviour can be observed in cases like moving a window with click-and-drag. The move plugin does not (probably, cannot) set the "from" workspace. Therefore when a window is moved, view-workspace-changed is emitted with garbage values for "from" workspace, much like the example above.

What can be done
For events like view-app-id-changed, we can completely ignore all the fields other than "app-id", but that is not the most ideal solution.

In general, it would be preferable to explicitly tell the user that the value of a field is invalid. For example, "wset-index" is, as a rule, never zero. The workspace indices can never be negative. So instead of letting garbage values being filled in, we can simply set them to these invalid values. This way, the events can be safely parsed and invalid values can be ignored.