Fix: repeated calls to Polygon.set_closed() might extend/truncate Polygon._path

Author: cgohlke

lib/matplotlib/patches.py

@@ -780,6 +780,8 @@ def get_closed(self):
         return self._closed
 
     def set_closed(self, closed):
+        if self._closed == bool(closed):
+            return
         self._closed = closed
         xy = self._get_xy()
         if closed: