fix(mailprotect): remove redundant db.close() causing "Cannot operate on a closed database

[Tokenzrey]

This PR fixes a critical bug in mailprotect.py that causes the artifact parser to crash when processing iOS < 13 Mail data.

The crash was caused by a redundant db.close() statement. Since the database is opened using a context manager (with open_sqlite_db_readonly...), the connection is automatically closed when the block exits. The explicit close call was creating a race condition or invalid state, leading to sqlite3.ProgrammingError: Cannot operate on a closed database.

Changes

• Removed: Redundant db.close() statement in mailprotect.py.
• Result: The parser now relies entirely on the context manager for resource cleanup, adhering to PEP8 best practices and preventing the crash.

Verification & Testing

I have created a reproduction script (test_mailprotect_fix.py) to verify the fix.

• Test Suite: 5/5 tests passed.
• Scenarios Covered:
  • Context Manager Lifecycle.
  • Multiple Queries within the same context.
  • Cursor recreation patterns.
  • Transaction handling.
  • Comparison of Original (Buggy) vs. Fixed patterns.

Test Output Summary:

TEST SUMMARY
================================================================================
Context Manager Lifecycle......................... [PASS]
Multiple Queries Within Context................... [PASS]
Cursor Recreation Pattern......................... [PASS]
Transaction Handling.............................. [PASS]
Original vs Fixed Pattern......................... [PASS]
================================================================================
Total: 5/5 tests passed
[SUCCESS] ALL TESTS PASSED - Fix is working correctly!

Checklist

• My code follows the style guidelines of this project.
• I have performed a self-review of my own code.
• I have verified the fix with a local test script.
• The changes generate no new warnings.

Related Issues

Closes #1386