fix(drawer): prevent TypeError when toggling with uninstantiated open drawer - #43326

Description

When a user clicks a drawer toggle button, the click handler closes any currently open drawer.
However, it previously called Drawer.getInstance(alreadyOpen)!.hide().
If the open drawer was not instantiated yet, getInstance() returned null.
The forced non-null assertion caused an unhandled TypeError: Cannot read properties of null (reading 'hide').
This issue occurred with server-rendered dialogs, native .showModal() calls, or drawer switches.

Additionally:

• The selector previously only matched dialog.drawer[open], ignoring responsive drawers like .md:drawer.
• If the toggle selector targeted an invalid or missing element, target was null.

Solution

1. Use Drawer.getOrCreateInstance(alreadyOpen).hide() instead of Drawer.getInstance(alreadyOpen)!.hide().
2. Use SELECTOR_OPEN so responsive open drawers are also matched.
3. Add a guard if (!target || isDisabled(this)) return to handle missing targets safely.

Motivation and Context

Fixes an unhandled JavaScript crash during drawer toggle interactions. Matches the safe instance resolution pattern used in js/src/dialog.ts.

How Has This Been Tested?

• Added automated unit tests in js/tests/unit/drawer.spec.js:
  • should not throw if another open drawer does not have a Drawer instance yet
  • should call hide first if another responsive drawer is open
  • should not throw if target element does not exist
• Ran Vitest suite: 70 passed out of 70 tests.
• Ran npm run js-lint: 0 errors.
• Ran npm run js-typecheck: 0 errors.