Fix empty xml document error.

Was getting the following errors when booting ST2 on OS X 10.8.5 after installing thios package:

```
Error parsing snippet xml: Error document empty. In file Packages/SaltStack-related syntax highlighting and snippets/Snippets/SaltStack/file.serialize.sublime-snippet
```

```
Error parsing snippet xml: Error document empty. In file Packages/SaltStack-related syntax highlighting and snippets/Snippets/SaltStack/file.blockreplace.sublime-snippet
```

```
Error parsing snippet xml: Error document empty. In file Packages/SaltStack-related syntax highlighting and snippets/Snippets/SaltStack/file.accumulated.sublime-snippet
```