Fixed libass 0.9.7 support.

b670356d introduced a segfault.
(cherry picked from commit e1cfb704)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/codec/libass.c

@@ -750,7 +750,7 @@ static ass_handle_t *AssHandleHold( decoder_t *p_dec )
     dialog_ProgressSet( p_dialog, NULL, 0.2 );
 #endif
 #if defined( LIBASS_VERSION ) && LIBASS_VERSION >= 0x00907000
-    ass_set_fonts( p_renderer, psz_font, psz_family, true, NULL, 0 );  // setup default font/family
+    ass_set_fonts( p_renderer, psz_font, psz_family, true, NULL, 1 );  // setup default font/family
 #else
     ass_set_fonts( p_renderer, psz_font, psz_family );  // setup default font/family
 #endif
@@ -760,7 +760,7 @@ static ass_handle_t *AssHandleHold( decoder_t *p_dec )
 #else
     /* FIXME you HAVE to give him a font if no fontconfig */
 #if defined( LIBASS_VERSION ) && LIBASS_VERSION >= 0x00907000
-    ass_set_fonts( p_renderer, psz_font, psz_family, false, NULL, 0 );
+    ass_set_fonts( p_renderer, psz_font, psz_family, false, NULL, 1 );
 #else
     ass_set_fonts_nofc( p_renderer, psz_font, psz_family );
 #endif