Fix tree iterator resizing of Color array

Setting the size of an array is best done with SetNumberOfValues(),
since Resize() only changes the allocation but not the number of
items present.

Common/DataModel/vtkTreeBFSIterator.cxx

@@ -49,7 +49,7 @@ void vtkTreeBFSIterator::Initialize()
     return;
   }
   // Set all colors to white
-  this->Color->Resize(this->Tree->GetNumberOfVertices());
+  this->Color->SetNumberOfValues(this->Tree->GetNumberOfVertices());
   for (vtkIdType i = 0; i < this->Tree->GetNumberOfVertices(); i++)
   {
     this->Color->SetValue(i, this->WHITE);

Common/DataModel/vtkTreeDFSIterator.cxx

@@ -65,7 +65,7 @@ void vtkTreeDFSIterator::Initialize()
     return;
   }
   // Set all colors to white
-  this->Color->Resize(this->Tree->GetNumberOfVertices());
+  this->Color->SetNumberOfValues(this->Tree->GetNumberOfVertices());
   for (vtkIdType i = 0; i < this->Tree->GetNumberOfVertices(); i++)
   {
     this->Color->SetValue(i, this->WHITE);