Fixes sabrogden#796

Fix clipboard data handling to prevent symbol insertion instead of copying links.

* **src/ClipboardViewer.cpp**
  - Correct the initialization of `m_activeWindowTitle` in `ValidActiveWnd` method.
  - Add a newline at the end of the file.

* **src/ClipboardSaveRestore.cpp**
  - Add checks to ensure clipboard data is valid before processing in `Save` and `Restore` methods.
  - Add checks to ensure clipboard data is valid before processing in multiple locations within the `Restore` method.
  - Add a newline at the end of the file.

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