Win32: WM_SETTINGCHANGE lParam Check for NULL

Check that lParam is non-NULL in WM_SETTINGCHANGE message handler.

See D14867 for details.

Differential Revision: https://developer.blender.org/D14867

Reviewed by Jesse Yurkovich

intern/ghost/intern/GHOST_SystemWin32.cpp

@@ -1987,7 +1987,8 @@ LRESULT WINAPI GHOST_SystemWin32::s_wndProc(HWND hwnd, UINT msg, WPARAM wParam,
           }
           break;
         case WM_SETTINGCHANGE:
-          if (wcscmp(LPCWSTR(lParam), L"ImmersiveColorSet") == 0) {
+          /* Microsoft: "Note that some applications send this message with lParam set to NULL" */
+          if ((lParam != NULL) && (wcscmp(LPCWSTR(lParam), L"ImmersiveColorSet") == 0)) {
             window->ThemeRefresh();
           }
           break;