Nick Craig-Wood 7f50143805 webdav: Fix free/used display for rclone about/df for certain backends - fixes #4348
Before this change if the server sent us xml like this

```
<D:propstat>
<D:prop>
<g0:quota-available-bytes/>
<g0:quota-used-bytes/>
</D:prop>
<D:status>HTTP/1.1 404 Not Found</D:status>
</D:propstat>
```

Rclone would read the empty XML items as containing 0

After this fix we make sure that we have a value before using it.
2020-06-20 15:16:14 +01:00
..
2020-05-12 15:56:50 +00:00
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2020-06-13 11:51:10 +01:00
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