please help i not understand with this

[weck25]

Uncaught TypeError: Cannot read property 'map' of undefined
at Example.render (app.js:66080)
at finishClassComponent (app.js:54665)
at updateClassComponent (app.js:54615)
at beginWork (app.js:56125)
at HTMLUnknownElement.callCallback (app.js:37693)
at Object.invokeGuardedCallbackDev (app.js:37742)
at invokeGuardedCallback (app.js:37797)
at beginWork$1 (app.js:60708)
at performUnitOfWork (app.js:59659)
at workLoopSync (app.js:59635)