fix(dock): handle nullish and missing parameters in resolveDockVisibility

[hsusul]

Fixes #1817

Problem

In src/helpers/dockPolicy.js:
resolveDockVisibility({ platform, controlPanelVisible }) threw TypeError: Cannot destructure property 'platform' of 'undefined' / 'null' when called without arguments or when passed null/undefined.

Solution

• Defaulted parameters with params || {} before destructuring.
• Added unit tests in test/helpers/dockPolicy.test.js.

Verification

• node --test test/helpers/dockPolicy.test.js (passes, 4/4 tests)
• npm run typecheck (passes, 0 errors)
• npm run lint (passes, 0 errors)
• npm run i18n:check (passes)
• npm run build:renderer (passes)
• git diff --check (clean)

[Chadpiha]

Thanks @hsusul! Closing with #1817 — same reasoning as the note on #1840.

dockPolicy.js is a deliberately pure policy module with exactly one caller (dockManager.js), which always passes { platform: process.platform, controlPanelVisible: this._controlPanelVisible } — a guaranteed string and a !!-coerced boolean. Nullish/missing params can't occur, and if a future refactor ever did pass them, the TypeError at the call site would be the more useful signal than a silent null.

Appreciate you reading through the dock policy code — thanks!