Reactjs 为什么我收到 Uncaught TypeError： Cannot read properties of null (reading 'add') on deployment

我正在使用fabric开发一个编辑器应用程序.js.在localhost上，当我单击Add Circle时，它可以正常工作，而在部署时，它会导致无法读取null的属性.

代码如下:

我正在使用react-context api，通过该api，我在画布中添加对象，并将其显示在屏幕上.

Fabriccircle.JS

import { fabric } from 'fabric';
import ContextCanvas from '../../../context/ContextCanvas';
import { Button } from '@chakra-ui/react';

const FabricTextBox = () => {
  const [canvas] = useContext(ContextCanvas);
  function addTextBox() {
    const textbox = new fabric.Textbox('Click on the Rectangle to move it.', {
      fontSize: 20,
      left: 50,
      top: 100,
      width: 200,
      fill: 'black',
      color: 'white',
      cornerColor: 'blue',

    });
    canvas.add(textbox);
    canvas.requestRenderAll();
  }
  return (
    <>
      <Button
        type="button"
        colorScheme="blue"
        onClick={addTextBox}
        variant={'ghost'}
        _hover={{}}
        _focus={{}}
        _active={{}}
        textColor={'white'}
        fontWeight={'light'}
      >
        Text Field
      </Button>
    </>
  );
};

export default FabricTextBox;

Fabriccanvas.JS

import React, { useContext, useLayoutEffect } from 'react';
import { fabric } from 'fabric';
import ContextCanvas from '../../context/ContextCanvas';


const FabricCanvas = () => {
  const [canvas, initCanvas] = useContext(ContextCanvas);


  useLayoutEffect(() => {

    return () => {
      initCanvas(new fabric.Canvas('c'));
    };
  }, []);


  return (
    <>
      <canvas
        id="c"
        width={window.innerWidth}
        height={window.innerHeight}
      />
    </>
  )
}
export default FabricCanvas;

ContextCanvas.js公司

import { fabric } from 'fabric';

const ContextCanvas = createContext();

export function CanvasProvider({ children }) {
  const [canvas, setCanvas] = useState(null);
  const initCanvas = c => {
    setCanvas(c);
    c.renderAll();
  };

  return (
    <ContextCanvas.Provider value={[canvas, initCanvas]}>
      {children}
    </ContextCanvas.Provider>
  );
}

export default ContextCanvas;