Fixed about_control_statements to pass tests

Learned about/that:
* if, then, else statements,
* nil would be returned if no true condition,
* condition operators.

[#65851764]
Fixed about_control_statements to pass tests

Learned about/that:
* statement modifiers,
* unless statement,
* and unless statement modifier.

[#65851764]
Fixed about_control_statements to pass tests

Learned about/that:
* while statement,
* break statement,
* break statement returns value,
* next statement,
* for statement.

[#65851764]