[escher] LayoutField: update the grey squares when using insertion

cursor

escher/src/layout_field.cpp

@@ -43,7 +43,9 @@ bool LayoutField::ContentView::setEditing(bool isEditing) {
 
 void LayoutField::ContentView::useInsertionCursor() {
   if (m_insertionCursor.isDefined()) {
+    m_cursor.layout().removeGreySquaresFromAllMatrixAncestors();
     m_cursor = m_insertionCursor;
+    m_cursor.layout().addGreySquaresToAllMatrixAncestors();
   }
 }
 

poincare/include/poincare/empty_layout.h

@@ -82,6 +82,7 @@ public:
     node()->setVisible(visible);
   }
 
+  EmptyLayoutNode::Color color() const { return node()->color(); }
   void setColor(EmptyLayoutNode::Color color) {
     node()->setColor(color);
   }