FreeType: fix NULL deref on embedded fonts (fixes #7771)

FT_Face.family_name can be NULL for embedded fonts.

See also http://www.freetype.org/freetype2/docs/reference/ft2-base_interface.html#FT_FaceRec
(cherry picked from commit d96f6e23adfd24ec188cb2a7b31cc2e992291172)

modules/text_renderer/freetype.c

@@ -1790,8 +1790,10 @@ static FT_Face LoadEmbeddedFace( filter_sys_t *p_sys, const text_style_t *p_styl
             {
                 int i_style_received = ((p_face->style_flags & FT_STYLE_FLAG_BOLD)    ? STYLE_BOLD   : 0) |
                                        ((p_face->style_flags & FT_STYLE_FLAG_ITALIC ) ? STYLE_ITALIC : 0);
-                if( !strcasecmp( p_face->family_name, p_style->psz_fontname ) &&
-                    (p_style->i_style_flags & (STYLE_BOLD | STYLE_ITALIC)) == i_style_received )
+                if( p_face->family_name != NULL
+                 && !strcasecmp( p_face->family_name, p_style->psz_fontname )
+                 && (p_style->i_style_flags & (STYLE_BOLD | STYLE_ITALIC))
+                                                          == i_style_received )
                     return p_face;
 
                 FT_Done_Face( p_face );