* Electron version: 1.7.5

### Expected behavior

When a theme color is no longer present the webContents did-change-theme-color event should return `null`.

### Actual behavior

The event returns `"#000000"`.

### How to reproduce

1. Log the returned color of the webContents did-change-theme-color event.
2. Go to https://electron.atom.io which has a theme color.
3. Go to https://atom.io which does not have a theme color.




atom/browser/api/atom_api_web_contents.cc
Emit("devtools-reload-page");
}
void WebContents::DevToolsFocused() {
  Emit("devtools-focused");
}
void WebContents::DevToolsOpened() {
  v8::Locker locker(isolate());
  v8::HandleScope handle_scope(isolate());
  auto handle = WebContents::CreateFrom(
      isolate(), managed_web_contents()->GetDevToolsWebContents());
  devtools_web_contents_.Reset(isolate(), handle.ToV8());
  
  base::Value tab_id(ID());
  managed_web_contents()->CallClientFunction(
      "DevToolsAPI.setInspectedTabId", &tab_id, nullptr, nullptr);
  
  if (owner_window())
    handle->SetOwnerWindow(managed_web_contents()->GetDevToolsWebContents(),
                           owner_window());
  Emit("devtools-opened");
}
void WebContents::DevToolsClosed() {