getStreamingData SWIG wrapper: return Py_None instead of empty dict

57d350d4d650160e3ab96a6c740f0c52fee29da5 fixed handling
of an empty streaming data dict, but external plugins
which call getStreamingData suffer from the same issue.
So work around it in the wrapper.
Update de.po

upgrade and reboot system was wrong
openvix: build 694
Merge remote-tracking branch 'pli/master'
rollback test
merge fix