Fix bug #4459

Since 4.X, there is a little bug when trying to click on a DB name expanded in the navigation tree.
To easily reproduce it, create a DB named "a". With the bug it's quite impossible to click on it when it's expanded. With the fix, it should be ok.
I suggest using "Databases with names less than three characters long aren't clickable when expanded" here. I can update the bug title in the tracker.