fix bug no ruler showup when no TPS data

closes #113 (closed)

sohstationviewer/view/plotting/time_power_squared_dialog.py

@@ -114,6 +114,7 @@ class TimePowerSquaredWidget(plotting_widget.PlottingWidget):
         self.plotting_axes.set_title(title, y=0, v_align='bottom')
 
         if self.plotting_data1 == {}:
+            self.is_working = False
             self.draw()
             self.clean_up('NO DATA')
             return