Editable Grid doesn't allow to edit the first row (Vaadin 8.4.2 )

Hi, I’m using Vaadin 8.4.2 and I found this issue:
I don’t able to edit the first row on editable grid.

I attach the source code:

@Theme("mytheme")
public class MyUI extends UI {

	@Override
    protected void init(VaadinRequest vaadinRequest) {
        final VerticalLayout layout = new VerticalLayout();
        
        ArrayList<Item> items = new ArrayList<Item>(); 
        InLineForm inline = new InLineForm(); 
        
        Grid<Item> grid = new Grid<Item>(Item.class);
        grid.setSizeFull();
        grid.setDataProvider(new ListDataProvider<>(items));
        grid.removeAllColumns();
        
        Binder<Item> binder = grid.getEditor().getBinder();
        Binding<Item, ?> binding1 =  binder.forField(inline.string1).bind("string1");
        Binding<Item, ?> binding2 = binder.forField(inline.string2).bind("string2");
        binder.bindInstanceFields(inline);
        
        grid.addColumn("string1").setEditorBinding(binding1);
        grid.addColumn("string2").setEditorBinding(binding2);;
        
        grid.getEditor().setEnabled(true); 
        grid.getEditor().setBuffered(false); 
        
        items.addAll(Arrays.asList(new Item("1","2"),new Item("3","4")));
        grid.getDataProvider().refreshAll();
        layout.addComponents(grid);
        
        setContent(layout);
    }

	public class InLineForm {
		public TextField string1 = new TextField();
		public TextField string2 = new TextField();
	}
		
	public class Item {
		
		
		public Item() {
		}
		
		public Item(String string1, String string2) {
			super();
			this.string1 = string1;
			this.string2 = string2;
		}

		public String string1; 
		
		public String string2;

		public String getString1() {
			return string1;
		}

		public void setString1(String string1) {
			this.string1 = string1;
		}

		public String getString2() {
			return string2;
		}

		public void setString2(String string2) {
			this.string2 = string2;
		} 
		
		

	}
	
	
	@WebServlet(urlPatterns = "/*", name = "MyUIServlet", asyncSupported = true)
	@VaadinServletConfiguration(ui = MyUI.class, productionMode = false)
	public static class MyUIServlet extends VaadinServlet {
	}

The result:
![Result]
(https://photos-3.dropbox.com/t/2/AAAbKsGZ_gFys2-fUu3lBFh7FQ1ParfuVptA29HIXNIIbA/12/812053/png/32x32/1/_/1/2/first_row_doesnt_editable.PNG/ENLAYxjO0canASACKAI/aL2pbYWwaoGydm4QIIOuhBC9_7__Hn7qoL5K__YO3kU?preserve_transparency=1&size=1600x1200&size_mode=3)

It was resolved on 8.4.3 Vaadin version and I also removed the follow line of code of .scss

.v-grid {
	.v-grid-header { 
		 	 border-bottom: 3px $v-focus-color solid;
			 }
	    }