Fix --lang bug in prepare-data.py
Fix --lang bug in prepare-data.py

The number of --lang arguments was checked against the actual extensions arguments list instead of its length

eske/word2vecpp-legacy,eske/multivec,eske/word2vecpp-legacy,eske/word2vecpp-legacy,eske/multivec,eske/word2vecpp-legacy,eske/multivec,eske/multivec,eske/multivec,eske/multivec,eske/word2vecpp-legacy