fix(v3/windows): guard FillRect against nil client rect in WM_ERASEBKGND

[taliesin-ai]

During minimise/restore transitions GetClientRect can legitimately return nil; passing that to FillRect crashes when painting the solid background in WM_ERASEBKGND. This guards the call.

Salvaged from #5636 — that PR's main change (moving resizePending to a per-window field) was superseded by #5596 (which removed the resize-debounce mechanism entirely) and #5616, but this nil-rect guard was a genuine, still-unfixed hardening. Credit to @sinspired for spotting it.

Builds clean for GOOS=windows.

Summary by CodeRabbit

• Bug Fixes
  • Fixed a Windows crash during minimize/restore transitions when the window client area was temporarily unavailable.
  • Fixed a macOS crash that could occur when screens changed.
  • Fixed a Linux (GTK4) issue where the native menu could fail to rebuild correctly.
• Chores
  • Updated the unreleased changelog with the latest fixes.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

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Reviewing files that changed from the base of the PR and between 3b35600 and 0694292.

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• v3/UNRELEASED_CHANGELOG.md

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Walkthrough

Adds a nil check in the Windows WM_ERASEBKGND handler so painting is skipped when GetClientRect returns nil, and updates the unreleased changelog with related fixed crash entries.

Changes

Windows repaint crash guard

Layer / File(s)	Summary
Nil rect guard and changelog v3/pkg/application/webview_window_windows.go, v3/UNRELEASED_CHANGELOG.md	WM_ERASEBKGND now checks GetClientRect for nil before calling FillRect; the changelog adds fixed bullets for GTK4 Linux, macOS, and Windows crash issues.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Possibly related PRs

• wailsapp/wails#5596: Changes the same Windows WM_ERASEBKGND painting path in webview_window_windows.go.
• wailsapp/wails#5616: Also touches Windows minimize/restore handling in webview_window_windows.go.
• wailsapp/wails#5683: Updates v3/UNRELEASED_CHANGELOG.md with overlapping unreleased fixed entries.

Suggested labels: Bug, Documentation, go, Windows, v3, v3-alpha, size:XS

Suggested reviewers: leaanthony, atterpac

Poem

A bunny saw a nil and said, “No paint today!”
The brush stayed tucked away, the crash hopped far away.
On Windows screens, the repaint path is lean and bright,
A tiny guard keeps minimise/restore safe tonight.
Hop hop, fixed! 🐇

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description summarizes the fix and context, but it omits the required fixed issue reference and most template sections.	Add the issue number with 'Fixes #' and fill the template sections for type of change, testing, and wails doctor output.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise and accurately describes the main change: guarding FillRect against a nil client rect in WM_ERASEBKGND.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch salvage-fillrect-guard-5636

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@v3/pkg/application/webview_window_windows.go`:
- Around line 1634-1638: The nil check in the paint path is ineffective because
`w32.GetClientRect` in `user32.go` panics on failure and never returns nil on
success, so the minimize/restore case still crashes before `FillRect` runs. Fix
this at the wrapper boundary by adding a non-panicking client-rect helper such
as `TryGetClientRect` or `GetClientRectOK` that returns both the `RECT` and a
success flag, then update the `w.hwnd` rendering code to use that helper and
skip painting when the call fails.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 8adc84a0-b907-44f1-a828-957f30a455b8

📥 Commits

Reviewing files that changed from the base of the PR and between 885963f and 3b35600.

📒 Files selected for processing (2)

• v3/UNRELEASED_CHANGELOG.md
• v3/pkg/application/webview_window_windows.go