parser yin BUGFIX ext instance has no stmt order restrictions

Fixes #1753
diff --git a/src/parser_yin.c b/src/parser_yin.c
index 3ea8f0b..28ae171 100644
--- a/src/parser_yin.c
+++ b/src/parser_yin.c
@@ -2869,6 +2869,11 @@
     assert(parrent == LY_STMT_MODULE || parrent == LY_STMT_SUBMODULE);
     enum yang_module_stmt gr, next_gr;
 
+    if (kw == LY_STMT_EXTENSION_INSTANCE) {
+        /* no order defined */
+        return LY_SUCCESS;
+    }
+
     LY_CHECK_RET(kw2kw_group(ctx, kw, &gr));
     LY_CHECK_RET(kw2kw_group(ctx, next_kw, &next_gr));