bugfix: remove value display item from graph before deletion

src/gui_qt/main/mainwindow.py

@@ -393,6 +393,8 @@ class NMRMainWindow(QtWidgets.QMainWindow, Ui_BaseWindow):
                             self.current_graph_widget.remove_external(item)
 
                     if val_figure == gid:
+                        self.current_graph_widget.remove_external(self.valuewidget.selection_real)
+                        self.current_graph_widget.remove_external(self.valuewidget.selection_imag)
                         self.tabWidget.setCurrentIndex(0)
 
                     self.current_graph_widget.enable_picking(False)