Core: Do not save changes of a text object if the GUI document is about to be closed

This fixes #16873: Text document breaks some Analysis container objects

src/Gui/TextDocumentEditorView.h

@@ -66,6 +66,7 @@ private:
     void labelChanged();
     void refresh();
     bool isEditorModified() const;
+    int execSaveDialog();
 
 private:
     QPlainTextEdit *const editor;