allow empty lists for loops

src/inja.hpp

@@ -380,6 +380,7 @@ public:
 	template<typename T = json>
   T eval_expression(const Parsed::ElementExpression& element, const json& data) {
 		const json var = eval_function(element, data);
+		if (var.empty()) return T();
 		try {
 			return var.get<T>();
 		} catch (json::type_error& e) {

test/src/unit-renderer.cpp

@@ -56,6 +56,9 @@ TEST_CASE("types") {
 		CHECK( env.render("{% for v in vars %}{% if v > 0 %}+{% endif %}{% endfor %}", data) == "+++" );
 		// CHECK( env.render("{% if 1 >= 18 %}test{% endif %}{% for v in vars %}{% if v > 0 %}+{% else %}-{% endif %}{% endfor %}", data) == "+++----" );
 
+		data["empty_loop"] = {};
+		CHECK( env.render("{% for name in empty_loop %}a{% endfor %}", data) == "" );
+
 		CHECK_THROWS_WITH( env.render("{% for name ins names %}a{% endfor %}", data), "[inja.exception.parser_error] unknown loop statement: for name ins names"  );
 		// CHECK_THROWS_WITH( env.render("{% for name in relatives %}{{ name }}{% endfor %}", data), "[inja.exception.json_error] [json.exception.type_error.302] type must be array, but is object"  );
 	}