Improve assertion and error handling

[eXpl0it3r]

Having taken a glance at the source code, it seems you use a lot of assert() calls. I can see that some are "correctly" used, e.g. when you check for a "contract", however there a lot of them are used for lazy error handling, which is in my opinion a rather bad practice and can lead to compiler warnings in release mode.

I personally prefer exceptions but some if statements would do the trick as well and if you just want to get rid of the compiler warning you could use some "unused macro".

[fallahn]

fair comment. I shall make an effort to tidy things up