reset tps_t after using to prevent bug when clicking on no point area

closes #275 (closed)

sohstationviewer/view/plotting/plotting_widget/plotting_widget.py

@@ -504,6 +504,9 @@ class PlottingWidget(QtWidgets.QScrollArea):
             if self.tps_t is None:
                 return
             xdata = self.tps_t
+            # Reset tps_t here because the reset in on_pick_event won't be
+            # reach when no point is clicked.
+            self.tps_t = None
         else:
             xdata = self.get_timestamp(event)