Various issues found by static analyzer

[v1993]

I've recently added cubosphere to https://lgtm.com and it have discovered a lot of issues, from medium to serious importance.

You can check full list of alerts at https://lgtm.com/projects/g/cubosphere/cubosphere-code.

I'm not working on cubosphere, but those issues are pretty serious and should be fixed first before continuing. Most of them are pretty trivial tho, so feel free to take on them in free time.

[v1993]

Now when errors and warnings are fixed, this is less critical. However, remaining problems still need attention.

I'll create branch lgtm-problems-recommendations-1. Push your work on this issue there (I'll probably go for few more fixes too).