Fix e2425b7: WidgetDimensions and depot sizes not set up if blitter forced.

Set up WidgetDimensions and depot sizes during InitWindowSystem().

src/window.cpp

@@ -1807,9 +1807,12 @@ void InitWindowSystem()
 	_scrolling_viewport = false;
 	_mouse_hovering = false;
 
+	SetupWidgetDimensions();
 	NWidgetLeaf::InvalidateDimensionCache(); // Reset cached sizes of several widgets.
 	NWidgetScrollbar::InvalidateDimensionCache();
 
+	InitDepotWindowBlockSizes();
+
 	ShowFirstError();
 }