Results: Fix KPC update where no sediment.

src/View/Results/PlotKPC.py

@@ -348,7 +348,9 @@ class PlotKPC(PamhyrPlot):
         if not self._init:
             self.draw()
 
-        self.update_bottom_with_bedload()
+        if reach.has_sediment():
+            self.update_bottom_with_bedload()
+
         self.update_water_elevation()
 
         self.update_idle()