Set immediate to true when calling _.debounce

When clicking on restore button for a minimized chat, the page's hash will change to `#`. It may cause problems for web apps that listen to changes in page's hash.

When `immediate` argument of `debounce` function is not set, `ev` is null and ev.preventDefault() will not be called.
Merge pull request #288 from arsh-co/master

Set immediate to true when calling _.debounce