[BUG] parse_args with empty vector crashes

[Tomdein]

I wanted to use this lib to parse args in cutom 'interactive console', so I used std::cin to read the input and split it into the std::vectorstd::string and run it in a loop.

But if you input empty line (just press enter) -> empty vector -> argparse crashes in parse_args_internal because the iterators are invalid with empty vector.

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You maybe want to do some sanity check for the input.

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I solved it in my code by just inserting the name of the command in front of the vector:
args.insert(args.begin(), "<program_name>");

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Is this an edge case? Yes
Did I spend way too much time on this because in my case I do not have access to debugger? Yes