[pango/fix-shape-tab-crash: 1/2] layout: Fix a crash

[Matthias Clasen <matthiasc src gnome org>]

commit 1f06c9154675fb6f956ecfadcf9dcdf790413c8e
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Jun 9 11:23:44 2020 -0400

    layout: Fix a crash
    
    pango_layout_get_effective_attributes can return
    NULL. But not all callers were handling that.

 pango/pango-layout.c | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)
---
diff --git a/pango/pango-layout.c b/pango/pango-layout.c
index 24444ed4..6d4d94cb 100644
--- a/pango/pango-layout.c
+++ b/pango/pango-layout.c
@@ -3083,17 +3083,22 @@ ensure_tab_width (PangoLayout *layout)
       PangoAttribute *attr;
       PangoAttrList *layout_attrs;
       PangoAttrList tmp_attrs;
-      PangoAttrIterator iter;
       PangoFontDescription *font_desc = pango_font_description_copy_static 
(pango_context_get_font_description (layout->context));
-      PangoLanguage *language;
+      PangoLanguage *language = NULL;
       PangoShapeFlags shape_flags = PANGO_SHAPE_NONE;
 
       if (pango_context_get_round_glyph_positions (layout->context))
         shape_flags |= PANGO_SHAPE_ROUND_POSITIONS;
 
       layout_attrs = pango_layout_get_effective_attributes (layout);
-      _pango_attr_list_get_iterator (layout_attrs, &iter);
-      pango_attr_iterator_get_font (&iter, font_desc, &language, NULL);
+      if (layout_attrs)
+        {
+          PangoAttrIterator iter;
+
+          _pango_attr_list_get_iterator (layout_attrs, &iter);
+          pango_attr_iterator_get_font (&iter, font_desc, &language, NULL);
+          _pango_attr_iterator_destroy (&iter);
+        }
 
       _pango_attr_list_init (&tmp_attrs);
 
@@ -3102,19 +3107,18 @@ ensure_tab_width (PangoLayout *layout)
       pango_attr_list_insert_before (&tmp_attrs, attr);
 
       if (language)
-       {
-         attr = pango_attr_language_new (language);
-         pango_attr_list_insert_before (&tmp_attrs, attr);
-       }
+        {
+          attr = pango_attr_language_new (language);
+          pango_attr_list_insert_before (&tmp_attrs, attr);
+        }
 
       items = pango_itemize (layout->context, " ", 0, 1, &tmp_attrs, NULL);
 
-      _pango_attr_iterator_destroy (&iter);
       if (layout_attrs != layout->attrs)
         {
-         pango_attr_list_unref (layout_attrs);
-         layout_attrs = NULL;
-       }
+          pango_attr_list_unref (layout_attrs);
+          layout_attrs = NULL;
+        }
       _pango_attr_list_destroy (&tmp_attrs);
 
       item = items->data;