minifier: block statements are not inlined in some cases

Compress
```js
function z(a) {
  {
    for (var i = 0; i < a; i++) {}
    console.log()
  }
  console.log()
}
```
into
```js
function z(a) {
  for (var i = 0; i < a; i++) {}
  console.log()
  console.log()
}
```
. This is safe because the block statement does not include lexical variable declarations.

If I remove the `for` loop or the `console.log` in the block, the block is inlined. 
