Teach IntelliJ IDEA some external nullness properties

- ArrayList#toArray() never returns null
- String#trim() never returns null
- StringUtils.split returns null iff its argument is null.
Protect against NPE when retrieving send2cgeo information

If there is an encoding error in the response, Network.getResponseData
will return null, which will in turn be returned by StringUtils.split.

There is no need to add more logging as the failure to retrieve the
response data will have been logged already.