round trip error using flow level and string with newline

The following fails:

```
yaml.safeLoad(yaml.safeDump({name: '\n'}, {flowLevel: 0}))
```

producing:

```
YAMLException: missed comma between flow collection entries at line 1, column 8:
    {name: |
           ^
```

The actual output is:

```
> console.log(y.safeDump({name: '\n'}, {flowLevel: 0}))
{name: |
}
```
