I had the same problem, and I solved with that, thanks!!!

I'm testing your bot, all options works fine except "3", buy_sell_bot... I'm getting this:

ruby bot.rb "STEEM" "3"

"https://bittrex.com/api/v1.1/public/getmarketsummary?market=BTC-STEEM"
[0.00045002, 0.000461, 0.00046071]
bot.rb:149:in buy_chunk': undefined method[]' for nil:NilClass (NoMethodError
)
from bot.rb:222:in buy_sell_bot' from bot.rb:260:in<'main>'

Help please