Create to_win if needed in Textord::make_spline_rows (fixes issue #3875)

There still remain memory leaks for the test scenario, but those are less
urgent as they are related to code which is only used for debugging.

Signed-off-by: Stefan Weil <[email protected]>

Author: stweil

src/textord/makerow.cpp

@@ -2000,6 +2000,9 @@ void Textord::make_spline_rows(TO_BLOCK *block, // block to do
                                bool testing_on) {
 #ifndef GRAPHICS_DISABLED
   ScrollView::Color colour; // of row
+  if (testing_on && to_win == nullptr) {
+    create_to_win(page_tr_);
+  }
 #endif
   TO_ROW_IT row_it = block->get_rows();