problem in concolic testing

[JacksonGL]

get exception after running the command: python scripts/jalangi.py concolic -i 100000 tests/fail_case

code of fail_case.js:

function foo(input){
    if(input[2] === 'r') {
        1;
    } else {
        2;
    }
}
foo();

exception I got:

---- Instrumenting ../tests/multiex/fail_case ----
Instrumenting ../tests/multiex/fail_case.js ...
==== Input 0 ====
---- Recording execution of tests/multiex/fail_case ----
fail_case_jalangi_.js
TypeError: Cannot read property '2' of undefined
    at Object.G (/Users/jacksongl/macos-workspace/research/jalangi/github_multiex/repository/jalangi/src/js/analysis.js:499:33)
    at foo (/Users/jacksongl/macos-workspace/research/jalangi/github_multiex/repository/jalangi/tests/multiex/fail_case_jalangi_.js:13:59)
    at invokeFun (/Users/jacksongl/macos-workspace/research/jalangi/github_multiex/repository/jalangi/src/js/analysis.js:451:37)
    at /Users/jacksongl/macos-workspace/research/jalangi/github_multiex/repository/jalangi/src/js/analysis.js:570:28
    at Object.<anonymous> (/Users/jacksongl/macos-workspace/research/jalangi/github_multiex/repository/jalangi/tests/multiex/fail_case_jalangi_.js:28:57)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Module.require (module.js:364:17)

---- Replaying tests/multiex/fail_case ----
./analyses/concolic/SymbolicEngine
TypeError: Cannot read property '2' of undefined
    at Object.G (/Users/jacksongl/macos-workspace/research/jalangi/github_multiex/repository/jalangi/src/js/analysis.js:499:33)
    at foo (/Users/jacksongl/macos-workspace/research/jalangi/github_multiex/repository/jalangi/tests/multiex/fail_case_jalangi_.js:13:59)
    at invokeFun (/Users/jacksongl/macos-workspace/research/jalangi/github_multiex/repository/jalangi/src/js/analysis.js:451:37)
    at /Users/jacksongl/macos-workspace/research/jalangi/github_multiex/repository/jalangi/src/js/analysis.js:570:28
    at Object.<anonymous> (/Users/jacksongl/macos-workspace/research/jalangi/github_multiex/repository/jalangi/tests/multiex/fail_case_jalangi_.js:28:57)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Module.require (module.js:364:17)