Fallback to 'kern' if no GPOS applied

src/hb-ot-shape.c

diff --git a/src/hb-ot-shape.c b/src/hb-ot-shape.c
index 795fd54..668b223 100644
--- a/src/hb-ot-shape.c
+++ b/src/hb-ot-shape.c
@@ -135,7 +135,7 @@
   for (i = 0; i < num_lookups; i++)
     hb_ot_layout_substitute_lookup (face, buffer, lookups[i], 0xFFFF);
 
-  return TRUE;
+  return num_lookups != 0;
 }
 
 hb_bool_t
@@ -161,5 +161,5 @@
 
   hb_ot_layout_position_finish (font, face, buffer);
 
-  return TRUE;
+  return num_lookups != 0;
 }