Check in hints.js if the object already exists (#61).

Revert "Fixed none removed hints on pages with AJAX (#61)."
This reverts commit 8570ead256e0e0d825e3c78c5db52d2b00c212e6.

Revert "Fixed none available hinting if vimb is started without JavaScript (#61)."
This reverts commit 14be33ebcbd1f0aa5ccd425655dc1d4d87899358.