Fails without error message when app doesn't have an icon

[rkbhochalya]

I tried to create DMG for an app under development to share it with friends and this tool simply returned red "x".

To find out the issue, I replaced process.exit(1) with throw error and got following error output:

TypeError: Cannot read property 'replace' of undefined
    at init (/Users/xxx/.config/yarn/global/node_modules/create-dmg/cli.js:82:47)
    at Object.<anonymous> (/Users/xxx/.config/yarn/global/node_modules/create-dmg/cli.js:190:1)
    at Module._compile (internal/modules/cjs/loader.js:1157:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1177:10)
    at Module.load (internal/modules/cjs/loader.js:1001:32)
    at Function.Module._load (internal/modules/cjs/loader.js:900:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:74:12)
    at internal/main/run_main_module.js:18:47

Looks like this is because the app doesn't have an icon yet. The tool should print a more useful error message in that case.