Catch network exceptions and return None instead of -1000

[kirichkov]

I've been testing this for 48 hours and I think it works well. Once in a while I get "Connection refused" by the controller, but I think the timeout has significantly improved the component's operation.

I've also replaced the -1000 value returned for inaccessible properties, because the correct one should be None. This should normally set the value to unavailable in the front end, which is more desirable than -1000. -1000 destroys the pretty graphs 😉