[plotter] correct a small bug in overlay sink

plotter.py

@@ -945,12 +945,11 @@ class Plotter(Aggregator, BaseProcessor):
         if sinks:
             try:
                 self.current_processor.sinks()
-                sinks = pd.DataFrame(
+                data = pd.DataFrame(
                     self.current_processor.get_value("/datasets/sinks")
                 )
-                part_pos = sinks[["x", "y", "z"]].values
+                part_pos = data[["x", "y", "z"]].values
                 unit_length /= self.current_processor.lbox
-                data = sinks
             except KeyError:
                 self.current_processor._log("No sinks particles", "WARNING")
                 return
@@ -1000,8 +999,7 @@ class Plotter(Aggregator, BaseProcessor):
         # Size and color
         if s is None and sinks:
             s = data.msink[mask] / 5e3
-
-        if s in data.keys():
+        elif s in data.keys():
             s = data[s][mask]
         elif callable(s):
             s = s(data)[mask]