Hide MainWindow toolbar's context menu

which just popped up an empty menu
Always preserve tags check state

If either None or Some or All tags are checked, we need to preserve
their check state. Also if a new tag is added in this situation, it
needs to become Checked so that it's  visible in the tags list, using
newTIDsToCheck.
Fixed bug in TagID returning from database

Everything was tagged with only ID=4 !! i.e the value of
QVariant::LongLong!