[sfnt] Another fix for buggy variation fonts.

Reported as

  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=759

* src/sfnt/sfobjs.c (sfnt_init_face): While setting number of
instances to zero for `CFF' fonts table, ensure that there is no
`CFF2' present also (which gets priority).

ChangeLog

@@ -1,3 +1,15 @@
+2017-03-08  Werner Lemberg  <wl@gnu.org>
+
+	[sfnt] Another fix for buggy variation fonts.
+
+	Reported as
+
+	  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=759
+
+	* src/sfnt/sfobjs.c (sfnt_init_face): While setting number of
+	instances to zero for `CFF' fonts table, ensure that there is no
+	`CFF2' present also (which gets priority).
+
 2017-03-07  Werner Lemberg  <wl@gnu.org>
 
 	[sfnt] Improve handling for buggy variation fonts.

src/sfnt/sfobjs.c

@@ -1058,8 +1058,10 @@
       FT_FREE( default_values );
       FT_FREE( instance_values );
 
-      /* we don't support Multiple Master CFFs yet */
+      /* we don't support Multiple Master CFFs yet; */
+      /* note that `glyf' or `CFF2' have precedence */
       if ( face->goto_table( face, TTAG_glyf, stream, 0 ) &&
+           face->goto_table( face, TTAG_CFF2, stream, 0 ) &&
            !face->goto_table( face, TTAG_CFF, stream, 0 ) )
         num_instances = 0;