remove space below tab bar, it has repaint issues (and wastes precious space)

src/gui/set/window.cpp

@@ -141,7 +141,7 @@ SetWindow::SetWindow(Window* parent, const SetP& set)
 	// tab bar, sizer
 	wxToolBar* tabBar = new wxToolBar(this, ID_TAB_BAR, wxDefaultPosition, wxDefaultSize, wxTB_FLAT | wxNO_BORDER | wxTB_HORIZONTAL | wxTB_HORZ_TEXT | wxTB_NOALIGN);
 	wxSizer* s = new wxBoxSizer(wxVERTICAL);
-	s->Add(tabBar, 0, wxEXPAND | wxBOTTOM, 3);
+	s->Add(tabBar, 0, wxEXPAND | wxBOTTOM, 0);
 	SetSizer(s);
 	#if defined(__WXMSW__) && defined(TBSTYLE_EX_DOUBLEBUFFER)
 		// Use double buffering