AttributeError: 'NoneType' object has no attribute 'canvas' when clicking on canvas

Question

The code is keep getting error when click on the canvas. How to fix this error? I would like to know where this error comes from. Thank you!Do I need to make a mouse clicking event? I would like to know what is a better way to fix this error.

import mplcursors
import numpy as np
from PyQt6.QtWidgets import QApplication, QSizePolicy, QWidget, QVBoxLayout
from matplotlib.figure import Figure
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas


class CustomCanvas(FigureCanvas):
    def __init__(self, parent=None):
        self.figure = Figure()
        super().__init__(self.figure)
        self.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Expanding)

    def draw_heatmap(self, data):
        self.figure.clear()
        ax = self.figure.add_subplot(111)
        heatmap = ax.imshow(data, cmap='coolwarm', interpolation='nearest', aspect='auto')
        self.figure.colorbar(heatmap)
        self.draw()

        cursor = mplcursors.cursor(heatmap, hover=True)

        @cursor.connect("add")
        def on_hover(sel):
            x, y = sel.index
            value = data[y, x]
            sel.annotation.set_text(f"Value: {value:.2f}")


class MainWindow(QWidget):
    def __init__(self):
        super().__init__()

        # Create the main layout
        main_layout = QVBoxLayout(self)

        # Create a custom canvas widget
        canvas = CustomCanvas()

        # Generate example heatmap data
        data = np.random.rand(10, 10)

        # Draw the heatmap
        canvas.draw_heatmap(data)

        # Add the canvas widget to the layout
        main_layout.addWidget(canvas)


if __name__ == '__main__':
    app = QApplication([])
    window = MainWindow()
    window.show()
    app.exec()

Here is the terminal showed:

Traceback (most recent call last):
  File "C:\Users\Python\Python311\Lib\site-packages\matplotlib\cbook\__init__.py", line 304, in process
    func(*args, **kwargs)
  File "C:\Users\Python\Python311\Lib\site-packages\matplotlib\offsetbox.py", line 1550, in on_release
    if self._check_still_parented() and self.got_artist:
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Python\Python311\Lib\site-packages\matplotlib\offsetbox.py", line 1560, in _check_still_parented
    self.disconnect()
  File "C:\Users\Python\Python311\Lib\site-packages\matplotlib\offsetbox.py", line 1568, in disconnect
    self.canvas.mpl_disconnect(cid)
    ^^^^^^^^^^^
  File "C:\Users\Python\Python311\Lib\site-packages\matplotlib\offsetbox.py", line 1517, in <lambda>
    canvas = property(lambda self: self.ref_artist.figure.canvas)
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'canvas'

enter image description here