title: resolveLocalFileSystemURL TypeError: Cannot read property 'then' of undefined TypeError
body: <p>I am working on ionic 4 ( capacitor ). I am trying to resolve a local file system URL so I used this function <code>resolveLocalFilesystemUrl</code> but unfortunately,  I am getting this error </p>
  
  <p><code>TypeError: Cannot read property 'then' of undefined TypeError: Cannot read property 'then' of undefined</code></p>
  
  <p>This is my code:
  <code>
      constructor(private _file: NativeFile) {}
  ...
  ..
            this._file.resolveLocalFilesystemUrl(nativeFilePath).then((entry: Entry) =&gt; {
     console.log(entry);
  });
  </code></p>
  
  <p>Note that this function returns a promise</p>