[Neo-CLI ] update the null check

[Jim8y]

Description

The Neo-CLI is nullable, however, the code still check if a non-null value is null or not, its not right.

And while doing this, I also reorganized the code to make it more clear for each section.

Fixes # (issue)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested? Running existing code

Test Configuration:

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[Jim8y]

I did not change the code but the null check. The reason that I updated so many codes is because i changed their order, make wallet close to wallet, block close to block.

If i do not make them together, i would have to open another pr to do it, a waste of your revewing efforts.