rdf validate skips empty frames if they occur before the first stream with stream options

[adanilenka]

Please refer to the test cases for input files: https://github.com/Jelly-RDF/jelly-protobuf/tree/GH-39-empty-frames

Example of the command with out_001.nt being an empty file:
jelly-cli rdf validate ./pos_015/in.jelly --compare-to-rdf-file ./pos_015/out_001.nt --compare-frame-indices=0 --compare-ordered=true

gives

Although the text format looks like: