Plot rendering error: 'NoneType' object has no attribute 'bbox'; metadata = {'Entries': 148975, 'Name': 'Chi2Dist-0', 'Overflow': 25.0, 'Type': 'Histo1d', 'Underflow': 0.0, 'loopStatus': [0, 500, 0, 0, 0], 'x': {'AxisTitle': 'Fit Chi/ndf', 'Bins': 51, 'High': 2.525, 'Low': -0.024999}, 'y': {'AxisTitle': 'Number of Pixels'}, 'z': {'AxisTitle': 'z'}}