backend.js:4999 Uncaught TypeError: Cannot read property 'spy' of undefined
    at setup (VM14490 backend.js:4999)
    at VM14490 backend.js:4256
    at Array.forEach (<anonymous>)
    at VM14490 backend.js:4254
    at Array.forEach (<anonymous>)
    at exports.default (VM14490 backend.js:4253)
    at handshake (VM14490 backend.js:4130)
    at helloListener (VM14490 backend.js:4171)
setup @ backend.js:4999
(anonymous) @ backend.js:4256
(anonymous) @ backend.js:4254
exports.default @ backend.js:4253
handshake @ backend.js:4130
helloListener @ backend.js:4171
postMessage (async)
listener @ contentScript.js:481
postMessage (async)
pingListener @ backend.js:4163
postMessage (async)
sendPing @ contentScript.js:462
338 @ contentScript.js:465
__webpack_require__ @ contentScript.js:20
(anonymous) @ contentScript.js:63
(anonymous) @ contentScript.js:66