Bug Fix

## 목적
Bug fix

## 작업 상세 내용
작업 내용 pull하여 make 실행 시 발견한 문제 해결 후 push

## Reference
(warning: unused variable 'key' [-Wunused-variable])

comparison of integer expressions of different signedness

warning: unused variable 'b'

'viewPortfolio' was not declared in this scope

4개 Bug Fix

The issue lists four compiler warnings/errors: unused variables 'key' and 'b', a signed/unsigned comparison, and an undeclared 'viewPortfolio'. Search the codebase for these identifiers using grep. Start by running 'make' to see the exact locations. Fix each warning by removing unused variables, fixing the type comparison, and ensuring 'viewPortfolio' is declared or included. Verify by rebuilding.

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