hooked_proc_fops: remove redundant struct check and handle null pointer

[AsafEitani]

Initial Checklist

• There is an issue describing the need for this PR.
• Git log contains summary of the change.
• Git log contains motivation and context of the change.
• If part of an EPIC, PR git log contains EPIC number.
• If part of an EPIC, PR was added to EPIC description.

Description (git log)

commit 7b9e6f3 (HEAD -> fix_fops, origin/fix_fops)
Author: AsafEitani eitaniasaf@gmail.com
Date: Tue Oct 25 17:22:16 2022 +0300

hooked_proc_fops: remove redundant struct check and handle null pointer

Fixes: #2300

Type of change

• Bug fix (non-breaking change fixing an issue, preferable).
• Quick fix (minor non-breaking change requiring no issue, use with care)
• Code refactor (code improvement and/or code removal)
• New feature (non-breaking change adding functionality).
• Breaking change (cause existing functionality not to work as expected).

How Has This Been Tested?

Tests being included in this PR:

• Tested on Ubuntu (where the bug wasn't reproduced to ensure that the detection still works)
• Tested on GKE to make sure that it solved the issue

Final Checklist:

Pick "Bug Fix" or "Feature", delete the other and mark appropriate checks.

• I have made corresponding changes to the documentation.
• My code follows the style guidelines (C and Go) of this project.
• I have performed a self-review of my own code.
• I have commented all functions/methods created explaining what they do.
• I have commented my code, particularly in hard-to-understand areas.
• My changes generate no new warnings.
• I have added tests that prove my fix, or feature, is effective.
• New and existing unit tests pass locally with my changes.
• Any dependent changes have been merged and published before.

[AlonZivony]

It seems good to me except for the size of array passed.

[yanivagman]

LGTM