TypeError occurs with custom resource Lambdas: Cannot read property 'Errors' of undefined

[eoinsha]

Describe the bug
If an application includes custom resources with their own Lambda functions, the function-specific configuration is missing and results in a TypeError:

  TypeError: Cannot read property 'Errors' of undefined
      at createLambdaAlarms (/Users/eoin/workspace/fourTheorem/slic-starter/user-service/node_modules/serverless-slic-watch-plugin/alarms-lambda.js:26:22)
      at Object.addAlarms (/Users/eoin/workspace/fourTheorem/slic-starter/user-service/node_modules/serverless-slic-watch-plugin/alarms.js:43:7)
      at ServerlessPlugin.finalizeHook (/Users/eoin/workspace/fourTheorem/slic-starter/user-service/node_modules/serverless-slic-watch-plugin/index.js:83:17)
      at PluginManager.runHooks (/Users/eoin/workspace/fourTheorem/slic-starter/node_modules/serverless/lib/classes/PluginManager.js:565:41)
      at async PluginManager.invoke (/Users/eoin/workspace/fourTheorem/slic-starter/node_modules/serverless/lib/classes/PluginManager.js:602:9)
      at async PluginManager.spawn (/Users/eoin/workspace/fourTheorem/slic-starter/node_modules/serverless/lib/classes/PluginManager.js:626:5)
      at async before:deploy:deploy (/Users/eoin/workspace/fourTheorem/slic-starter/node_modules/serverless/lib/plugins/deploy.js:61:11)
      at async PluginManager.runHooks (/Users/eoin/workspace/fourTheorem/slic-starter/node_modules/serverless/lib/classes/PluginManager.js:565:35)
      at async PluginManager.invoke (/Users/eoin/workspace/fourTheorem/slic-starter/node_modules/serverless/lib/classes/PluginManager.js:602:9)
      at async PluginManager.run (/Users/eoin/workspace/fourTheorem/slic-starter/node_modules/serverless/lib/classes/PluginManager.js:663:7)
      at async Serverless.run (/Users/eoin/workspace/fourTheorem/slic-starter/node_modules/serverless/lib/Serverless.js:464:5)
      at async /Users/eoin/.n/lib/node_modules/serverless/scripts/serverless.js:830:9

To Reproduce
Using the slic-watch branch of SLIC Starter (https://github.com/fourTheorem/slic-starter)
sls package --region=eu-west-1 --stage stg in /user-service

Expected behavior
Alarms are created and packaged