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* [X] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project adheres to.
* [X] I have searched the issue tracker for an issue that matches the one I want to file, without success.

### Issue Details

* **Electron Version:**
```
10.0.0-nightly.20200327 < GTK dialog does open, crashes after dialog closes
10.0.0-nightly.20200326 < GTK dialog doesn't open, crashes after multiple button clicks
10.0.0-nightly.20200325 < GTK dialog doesn't open, crashes after multiple button clicks
10.0.0-nightly.20200324 < GTK dialog doesn't open, crashes after multiple button clicks
10.0.0-nightly.20200323 < GTK dialog doesn't open, crashes after multiple button clicks
10.0.0-nightly.20200320 < GTK dialog doesn't open, crashes after multiple button clicks
10.0.0-nightly.20200317 < GTK dialog doesn't open, crashes after multiple button clicks
10.0.0-nightly.20200310 < Working as expected
```
* **Operating System:**
Ubuntu 18.04 x64
* **Last Known Working Electron version:**


### Expected Behavior
<!-- A clear and concise description of what you expected to happen. -->
I expect to be able to use the GTK FileChooser to upload/download files.

### Actual Behavior
<!-- A clear and concise description of what actually happened. -->
From nightly version `10.0.0-nightly.20200317` the electron window closes without showing the file GTK FileChooser and reports a SEGFAULT in the terminal window. 

From nightly version `10.0.0-nightly.20200327` the GTK FileChooser opens, but after opening a file or cancelling, the electron window exits and reports a SEGFAULT in the terminal window.

### To Reproduce
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`electron  http://jsfiddle.net/lovlka/N4Jxk/`

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### Screenshots
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### Additional Information

shell/browser/ui/file_dialog_gtk.cc
gin_helper::Promise<gin_helper::Dictionary> promise) {
  GtkFileChooserAction action = GTK_FILE_CHOOSER_ACTION_OPEN;
  if (settings.properties & OPEN_DIALOG_OPEN_DIRECTORY)
    action = GTK_FILE_CHOOSER_ACTION_SELECT_FOLDER;
  FileChooserDialog* open_dialog = new FileChooserDialog(action, settings);
  open_dialog->SetupOpenProperties(settings.properties);
  open_dialog->RunOpenAsynchronous(std::move(promise));
}
bool ShowSaveDialogSync(const DialogSettings& settings, base::FilePath* path) {
  FileChooserDialog save_dialog(GTK_FILE_CHOOSER_ACTION_SAVE, settings);
  save_dialog.SetupSaveProperties(settings.properties);
  gtk_widget_show_all(save_dialog.dialog());
  int response = gtk_dialog_run(GTK_DIALOG(save_dialog.dialog()));
  if (response == GTK_RESPONSE_ACCEPT) {
    *path = save_dialog.GetFileName();
    return true;
  }
  return false;
}
void ShowSaveDialog(const DialogSettings& settings,
                    gin_helper::Promise<gin_helper::Dictionary> promise) {
  FileChooserDialog* save_dialog =
      new FileChooserDialog(GTK_FILE_CHOOSER_ACTION_SAVE, settings);
  save_dialog->RunSaveAsynchronous(std::move(promise));
}
}