Attempting to set the window title of a BrowserDock that is closed, then
opening the BrowserDock, would show that BrowserDock with an incorrect
title. We can handle this by overriding the showEvent of BrowserDock and
manually setting the window title after the showEvent is called,
hopefully ensuring that we are only setting the window title on a window
that exists.
Works around a bug in Qt where setWindowTitle called on a native window
that hasn't been initialised yet causes the title data to be lost,
resulting in the window's title never being set.
Users don't realize that dockable windows can be closed (hidden) and can
be shown again via the View menu. This adds an explicit warning when
the user first closes a dockable window for their first time. In future
versions, this should be changed to a dialog box with a "Do not show
again" checkbox.