Spoils titles with LaTeX characters (e.g. non-English characters)

E.g. for an entry with title:

```
title = {{Mafia, zdradziecka parzysto\'{s}\'{c} oraz pi}}
```

it produces:

```
'title': 'Mafia , zdradziecka parzysto\\ { s } \\ { c } oraz pi'
```

where it would be desirable to have its original form, i.e.:

```
'title': 'Mafia , zdradziecka parzysto\'{s}\'{c} oraz pi'
```
