[pango/survive-without-fonts] layout: Try harder to survive without fonts

[Matthias Clasen <matthiasc src gnome org>]

commit c90d22ca5887612cbbf8a050bb4a1a25727b4230
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Apr 8 16:33:56 2022 -0400

    layout: Try harder to survive without fonts
    
    No great typography can be expected without fonts,
    but we should try not to crash, since this situation
    can apparently happen on Windows.
    
    Fixes: #680

 pango/pango-layout.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
---
diff --git a/pango/pango-layout.c b/pango/pango-layout.c
index eb674b50..6d9bb12a 100644
--- a/pango/pango-layout.c
+++ b/pango/pango-layout.c
@@ -6624,7 +6624,7 @@ collect_baseline_shift (ParaBreakState *state,
                   int subscript_y_offset = 0;
 
 
-                  if (prev)
+                  if (prev && prev->analysis.font)
                     {
                       hb_font_t *hb_font = pango_font_get_hb_font (prev->analysis.font);
                       hb_ot_metrics_get_position (hb_font, HB_OT_METRICS_TAG_SUPERSCRIPT_EM_Y_OFFSET, 
&superscript_y_offset);
@@ -6716,7 +6716,12 @@ apply_baseline_shift (PangoLayoutLine *line,
       hb_tag_t lang_tags[HB_OT_MAX_TAGS_PER_LANGUAGE];
       unsigned int script_count = HB_OT_MAX_TAGS_PER_SCRIPT;
       unsigned int lang_count = HB_OT_MAX_TAGS_PER_LANGUAGE;
+#endif
+
+      if (item-analysis.font == NULL)
+        continue;
 
+#if HB_VERSION_ATLEAST(4,0,0)
       hb_font = pango_font_get_hb_font (item->analysis.font);
 
       script = (hb_script_t) g_unicode_script_to_iso15924 (item->analysis.script);