Bug 1657542

Description of problem:
Segmentation error in pango_fc_font_key_get_variations().

Version-Release number of selected component (if applicable):
pango-1.42.4-1.fc29

How reproducible:
I can reproduce it with a non opensource application that started to crash
after updating my Fedora 27 to Fedora 29.
The application is eclipse based; same problem has been reported for MATLAB.

Steps to Reproduce:
Have the application do some rendering involving fonts.

Actual results:
Crash.

Expected results:
Normal content display.

Additional info:

Problem already well known; see:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=898960
https://bugs.gentoo.org/671136
https://github.com/gentoo/gentoo/pull/10417

The gentoo patch actually solved the problem when applied
to pango-1.42.4-1.fc29 (I got fixed packages by running mock).

diff --git a/pango/pangofc-shape.c b/pango/pangofc-shape.c
index a59ca67c..53269d73 100644
--- a/pango/pangofc-shape.c
+++ b/pango/pangofc-shape.c
@@ -380,8 +380,10 @@ _pango_fc_shape (PangoFont           *font,
                    fc_font->is_hinted ? ft_face->size->metrics.x_ppem : 0,
                    fc_font->is_hinted ? ft_face->size->metrics.y_ppem : 0);
 
-  variations = pango_fc_font_key_get_variations (key);
-  if (variations)
+  if (key)
+  {
+    variations = pango_fc_font_key_get_variations (key);
+    if (variations)
     {
       guint n_variations;
       hb_variation_t *hb_variations;
@@ -391,6 +393,7 @@ _pango_fc_shape (PangoFont           *font,
 
       g_free (hb_variations);
     }
+  }
 
   hb_buffer = acquire_buffer (&free_buffer);