#### Describe the bug
The irrelevant error returned when requesting illegal URL, like: "tel:484-695-3408"
```
TypeError: Cannot read property 'replace' of null
    at dispatchHttpRequest (node_modules/axios/lib/adapters/http.js:109:74)
    at new Promise (<anonymous>)
    at httpAdapter (node_modules/axios/lib/adapters/http.js:46:10)
    at dispatchRequest (node_modules/axios/lib/core/dispatchRequest.js:52:10)
```

#### To Reproduce
```js
axios.get('tel:484-695-3408').catch(err => console.error(err));
```

#### Expected behavior
Return descriptive error, like "Unsupported protocol tel:"

#### Environment
 - Axios Version: 0.21.1
 - Adapter: HTTP
 - Browser: none
 - Browser Version: none
 - Node.js Version: 12.19.0
 - OS: MacOS 10.14
 - Additional Library Versions: none

#### Additional context/Screenshots
none
lib/adapters/http.js
statusText: res.statusMessage,
        headers: res.headers,
        config: config,
        request: lastRequest
      };
      if (config.responseType === 'stream') {
        response.data = stream;
        settle(resolve, reject, response);
      } else {
        var responseBuffer = [];
        var totalResponseBytes = 0;
        stream.on('data', function handleStreamData(chunk) {
          responseBuffer.push(chunk);
          totalResponseBytes += chunk.length;
          
          if (config.maxContentLength > -1 && totalResponseBytes > config.maxContentLength) {
            
            rejected = true;
            stream.destroy();
            reject(createError('maxContentLength size of ' + config.maxContentLength + ' exceeded',
              config, null, lastRequest));
          }
        });
        stream.on('aborted', function handlerStreamAborted() {
          if (rejected) {
            return;
          }
          stream.destroy();
          reject(createError('error request aborted', config, 'ERR_REQUEST_ABORTED', lastRequest));
        });