### Website or app

google.com

### Repro steps

This started after last update 4.20.0
![image](https://user-images.githubusercontent.com/11052469/137713404-e6702959-7870-46a6-8566-4cfe61d25309.png)
![image](https://user-images.githubusercontent.com/11052469/137713464-c5e478d2-4e9e-4ee4-abdf-83d23c04704b.png)


### How often does this bug happen?

Every time

### DevTools package (automated)

_No response_

### DevTools version (automated)

_No response_

### Error message (automated)

_No response_

### Error call stack (automated)

_No response_

### Error component stack (automated)

_No response_

### GitHub query string (automated)

_No response_
);
    }
    return;
  }
  switch (data.source) {
    case 'react-devtools-detector':
      lastDetectionResult = {
        hasDetectedReact: true,
        reactBuildType: data.reactBuildType,
      };
      chrome.runtime.sendMessage(lastDetectionResult);
      break;
    case 'react-devtools-extension':
      if (data.payload?.type === 'fetch-file-with-cache') {
        const url = data.payload.url;
        const reject = value => {
          chrome.runtime.sendMessage({
            source: 'react-devtools-content-script',
            payload: {
              type: 'fetch-file-with-cache-error',
              url,
              value,
            },
          });
        };
        const resolve = value => {
          chrome.runtime.sendMessage({
            source: 'react-devtools-content-script',
            payload: {
              type: 'fetch-file-with-cache-complete',