Fix out-of-range exceptions during the parsing of circuit strings.

[snowhaze]

Prevent the issues which required the many try / catches in v400.6.2.

[tladesignz]

I have to admit, I feel embarrassed. Your changes are beautiful and that's how I should have written it in the first place. Thanks a lot and congratulations: I don't remember something like that happening to me ever before. 👍