fix: Check Intptr and HwndSource isn't Zero before using in TitleBar

[jbryknar]

Pull request type

Please check the type of change your PR introduces:

• Update
• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes

What is the current behavior?

• When the user holds down the ESC key while a message box is open, the application crashes.
• Rapidly closing the window immediately after it appears leads to an “HWND = 0” error.
• In contrast, explicitly setting the window’s content to null does not cause a crash.

Issue Number: #1383

What is the new behavior?

• Before interacting with a window, the code now verifies that the HWND value is non-zero, preventing invalid handle usage.
• When attaching hooks, it first confirms that the HwndSource instance is not null, ensuring it only adds hooks to valid sources.
• As a result, holding ESC key or rapidly closing the message box no longer triggers crashes or “HWND = 0” errors.