Support subexpressions in construct()

lib/construct.c

@@ -74,7 +74,8 @@ static void construct_term(const regex_term_t *term, fsa_t *out)
 		construct_literal(term->literal, out);
 		break;
 	case REGEX_TERM_SUBEXPR:
-		return;
+		construct(&term->subexpr, out);
+		break;
 	case REGEX_TERM_WILDCARD:
 	case REGEX_TERM_CLASS:
 		assert(false);