del over nonexistent path will create every step except the last that purports to delete  

An example is this:

```js
import immutable from 'object-path-immutable';

const obj = { foo: { bar: true } };
const newObj = immutable.del(obj, 'foo.rab.oof'); 
```

What one gets is
```js
{ foo: { bar: true, rab: { } }
```

The expected behavior is
```js
{ foo: { bar: true } }
```