fix(core): resolve 17 security and quality bugs from full code audit - #516

Non-nullable field 'tt' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

Converting null literal or possible null value to non-nullable type.

Converting null literal or possible null value to non-nullable type.

Converting null literal or possible null value to non-nullable type.

Non-nullable field 'baseStream' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

Non-nullable field 'ftab' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

Non-nullable field 'szptr' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

Non-nullable field 'zptr' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

Non-nullable field 'quadrant' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.