Fail to resolve

7:59:46 AM - error:  message=Cannot read property '_source' of undefined, stack=TypeError: Cannot read property '_source' of undefined
    at ElasticSearchTransformer.<anonymous> (/usr/local/app/src/elastic-search-transformer.ts:95:46)
    at Generator.next (<anonymous>)
    at fulfilled (/usr/local/app/dist/elastic-search-transformer.js:4:58)
    at process._tickCallback (internal/process/next_tick.js:68:7)
(node:1) UnhandledPromiseRejectionWarning: TypeError: Cannot read property '_source' of undefined
    at ElasticSearchTransformer.<anonymous> (/usr/local/app/src/elastic-search-transformer.ts:95:46)
    at Generator.next (<anonymous>)
    at fulfilled (/usr/local/app/dist/elastic-search-transformer.js:4:58)
    at process._tickCallback (internal/process/next_tick.js:68:7)