Update decompressor.cpp

[no-one-21]

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[srbcheema1]

good catch @no-one-21,
You have found the location of the problem easily. there is some problem in implementing the technique.
Whenever you solve an issue try to figure the main cause of the issue. not the only one described in description.
it is good to discover other cases than given in the discription of issue. I have written that it fails on empty file but that was not the only problem. I have left the other cases for the solvers. you did really well by finding out the location of the problem.
The other cases are that it will also fail on file size less than 5 words (not only empty file). Sometimes it happens that issue reporter reports the issue with less information it is duty of contributers to detect the root cause of problem and try to fix all the cases including those not listed in issue

One more thing never miss description of you PR
Good luck and I hope to see another commit over this PR :)