Fix Find Dialog

It should be centered at initialization. It does not matter that selectedJoshText is null Java will interpret that as centering it to the screen. This is what it was doing in old LateralGM versions and I have gone back and tested. If LateralGM wants it to start relative to its main frame it should handle that, but for the sake of JoshEdit it should by default be set relative to the screen or the selected JoshText.