[poincare] DynLayout: Do not detach children needing to be deleted

Change-Id: Id46afd541c8090268e7f48f09a07e6cb6240f445

poincare/include/poincare/dynamic_layout_hierarchy.h

@@ -35,6 +35,8 @@ public:
 protected:
   const ExpressionLayout ** m_children;
   int m_numberOfChildren;
+private:
+  void removeDetachedChildren();
 };
 
 }

poincare/src/layout/dynamic_layout_hierarchy.cpp

@@ -46,7 +46,7 @@ void DynamicLayoutHierarchy::mergeChildrenAtIndex(DynamicLayoutHierarchy * eL, i
     }
   }
   addChildrenAtIndex(eL->children(), eL->numberOfChildren(), indexForInsertion, removeEmptyChildren);
-  eL->detachChildren();
+  eL->removeDetachedChildren();
   delete eL;
 }
 
@@ -160,4 +160,14 @@ void DynamicLayoutHierarchy::removeAndDeleteChildren() {
   m_numberOfChildren = 0;
 }
 
+void DynamicLayoutHierarchy::removeDetachedChildren() {
+  int currentIndex = 0;
+  for (int i = 0; i < m_numberOfChildren; i++) {
+    if (m_children[i] != nullptr && m_children[i]->parent() == this) {
+      m_children[currentIndex++] =  m_children[i];
+    }
+  }
+  m_numberOfChildren = currentIndex;
+}
+
 }