Undid last commit and restored bool argument to wxFrame::DoGiveHelp() as

removing it could silently break existing user code overriding this function.

Fix the problem with not restoring the original status bar text when the mouse
pointer left the toolbar by simply calling DoGiveHelp() with false as second
parameter only if there was no valid tool under mouse, not if the help string
(for a valid tool) was empty.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@45240 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775