libparse: fix space before closing paren in expressions

tests/unit/techmap/libparseTest.cc

@@ -13,7 +13,7 @@ namespace RTLIL {
 		void checkAll(std::initializer_list<std::string> expressions, std::string expected) {
 			for (const auto& e : expressions) {
 				auto helper = LibertyExpression::Lexer(e);
-				auto tree_s = LibertyExpression::parse(helper).str();
+				auto tree_s = LibertyExpression::parse(helper).sexpr_str();
 				EXPECT_EQ(tree_s, expected);
 			}
 		}
@@ -82,6 +82,11 @@ namespace RTLIL {
 		}, "(and (pin \"x\")\n"
 		   "     (not (pin \"y\")))"
 		);
+		checkAll({
+			"( D & EN )",
+		}, "(and (pin \"D\")\n"
+		   "     (pin \"EN\"))"
+		);
 	}
 }