[wasm] Return empty object when ref2obj fails

src/hb-wasm-api-face.hh

@@ -39,8 +39,6 @@ face_reference_table (HB_WASM_EXEC_ENV_COMPOUND
   HB_RETURN_TYPE (blob_t, blob);
 
   HB_REF2OBJ (face);
-  if (unlikely (!face))
-    return;
 
   blob.length = 1;
 }

src/hb-wasm-api-font.hh

@@ -36,8 +36,6 @@ font_get_face (HB_WASM_EXEC_ENV
 	       font_t fontref)
 {
   HB_REF2OBJ (font);
-  if (unlikely (!font))
-    return nullref;
 
   hb_face_t *face = hb_font_get_face (font);
 
@@ -46,7 +44,6 @@ font_get_face (HB_WASM_EXEC_ENV
 }
 
 
-
 }}
 
 #endif /* HB_WASM_FONT_HH */

src/hb-wasm-api.hh

@@ -64,7 +64,7 @@ HB_INTERNAL extern hb_user_data_key_t _hb_wasm_ref_type_key;
     /* This works because all our objects have the same hb_object_t layout. */ \
     if (unlikely (hb_##obj##_get_user_data (obj, &_hb_wasm_ref_type_key) != \
 		  (void *) hb_wasm_ref_type_##obj)) \
-      obj = nullptr; \
+      obj = hb_##obj##_get_empty (); \
   } HB_STMT_END
 #define HB_OBJ2REF(obj) \
   uint32_t obj##ref = nullref; \