### Godot version

v4.0.beta17.mono.official [c40020513]

### System information

Windows 11 22H2

### Issue description

If a focused subwindow is destroyed, DisplayServerWindows may still attempt to send mouse motion events to that window, because `last_focused_window` isn't updated until another window is focused.

```
ERROR: Condition "!windows.has(p_window)" is true. Returning: Point2i()
   at: window_get_position (platform/windows/display_server_windows.cpp:999)
```

### Steps to reproduce

Run the MRP, click some non-Godot application window to focus it, then click the "CLOSE" button in the secondary window. This destroys the window without re-focusing the main window, so hovering the mouse over the main window will produce the error message above.

### Minimal reproduction project

[native_windows_hover.zip](https://github.com/godotengine/godot/files/10573386/native_windows_hover.zip)

if (prev_wc != 0) {
							ERR_PRINT("invalid utf16 surrogate input");
						}
						prev_wc = unicode;
						break; 
					} else if ((unicode & 0xfffffc00) == 0xdc00) {
						if (prev_wc == 0) {
							ERR_PRINT("invalid utf16 surrogate input");
							break; 
						}
						unicode = (prev_wc << 10UL) + unicode - ((0xd800 << 10UL) + 0xdc00 - 0x10000);
						prev_wc = 0;
					} else {
						prev_wc = 0;
					}
					Ref<InputEventKey> k;
					k.instantiate();
					Key keycode = KeyMappingWindows::get_keysym(MapVirtualKey((ke.lParam >> 16) & 0xFF, MAPVK_VSC_TO_VK));
					Key key_label = keycode;
					Key physical_keycode = KeyMappingWindows::get_scansym((ke.lParam >> 16) & 0xFF, ke.lParam & (1 << 24));
					static BYTE keyboard_state[256];
					memset(keyboard_state, 0, 256);
					wchar_t chars[256] = {};
					UINT extended_code = MapVirtualKey((ke.lParam >> 16) & 0xFF, MAPVK_VSC_TO_VK_EX);
					if (!(ke.lParam & (1 << 24)) && ToUnicodeEx(extended_code, (ke.lParam >> 16) & 0xFF, keyboard_state, chars, 255, 4, GetKeyboardLayout(0)) > 0) {
						String keysym = String::utf16((char16_t *)chars, 255);
						if (!keysym.is_empty()) {
							key_label = fix_key_label(keysym[0], keycode);
						}
					}