Fix button inconsistencies in app.topbar.component.html

[clockwinder]

I noticed inconsistent button behavior in the UI, and after making an issue I looked into the problem and it seemed like an easy enough fix for my to take a crack at.

Fixes: https://github.com/adityachandelgit/BookLore/issues/541

I'm no expert, so please let me know if I've made any mistakes here, this is one of my first PRs on a public project!