functions defined inside "if" statement are not correctly processed

[hubo1016]

Bug report or feature request?

Bug

ES5 or ES6+ input?

ES5

Uglify version (uglifyjs -V)

uglify-js 3.3.13

JavaScript input

function test(a){
    if(a){
        function test2(x){
            return a + x;
        }
    }else{
        function test2(x){
            return x;
        }
    }
    return test2(1);
}

The uglifyjs CLI command executed or minify() options used.

uglifyjs --compress -- ./test.js

JavaScript output or error produced.

function test(a){if(a);else;return 1}

[alexlamsl]

The example behaves correctly when run on JavaScript platforms, i.e. when not interpreted as ES6+

See #1666.