Set path attr in case ErrorBarItem initialized without data

pyqtgraph/graphicsItems/ErrorBarItem.py

@@ -59,6 +59,7 @@ class ErrorBarItem(GraphicsObject):
         
         x, y = self.opts['x'], self.opts['y']
         if x is None or y is None:
+            self.path = p
             return
         
         beam = self.opts['beam']
@@ -146,4 +147,4 @@ class ErrorBarItem(GraphicsObject):
             self.drawPath()
         return self.path.boundingRect()
     
-        
+