Fix: Navring error

introduced with this commit
https://github.com/SlimRoms/frameworks_base/commit/8c8769815c0f1e58657e4e31ef7f7014e45b0831
the placeholders react on touch which ends up in open gnow permanently
disable the placeholders. Sorry for that

as well a small change (even if this case should never happen) to
be 100% sure the listeners are attached before unregistering

cheers

Change-Id: Iab783861020ed03645d60aa7e121edee29688841