#### 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
test/unit/adapters/http.js
});
    });
  });
  it('should support gunzip error handling', function (done) {
    server = http.createServer(function (req, res) {
      res.setHeader('Content-Type', 'application/json');
      res.setHeader('Content-Encoding', 'gzip');
      res.end('invalid response');
    }).listen(4444, function () {
      axios.get('http://localhost:4444/').catch(function (error) {
        done();
      });
    });
  });
  it('should support disabling automatic decompression of response data', function(done) {
    var data = 'Test data';
    zlib.gzip(data, function(err, zipped) {
      server = http.createServer(function(req, res) {
        res.setHeader('Content-Type', 'text/html;charset=utf-8');
        res.setHeader('Content-Encoding', 'gzip');
        res.end(zipped);
      }).listen(4444, function() {
        axios.get('http://localhost:4444/', {
          decompress: false,
          responseType: 'arraybuffer'
        }).then(function(res) {
          assert.equal(res.data.toString('base64'), zipped.toString('base64'));
          done();
        });
      });