[CAT-289] 집중 시간 저장 · Nexters/Mohanyang-iOS@4b2648a

Force casts should be avoided (force_cast)

Implicitly unwrapped optionals should be avoided when possible (implicitly_unwrapped_optional)

Force unwrapping should be avoided (force_unwrapping)

Force casts should be avoided (force_cast)

Force casts should be avoided (force_cast)

Force unwrapping should be avoided (force_unwrapping)

Force unwrapping should be avoided (force_unwrapping)

Don't include vertical whitespace (empty line) after opening braces (vertical_whitespace_opening_braces)

Don't include vertical whitespace (empty line) after opening braces (vertical_whitespace_opening_braces)

Initializing an optional variable with nil is redundant (redundant_optional_initialization)

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