This is a bug report in webpack 3.4.1 (and webpack@beta).
What is the current behavior?
In the following gist there are two configs, one depending on another. If you provide an incorrect dependency name, the error message is
Cannot read property 'hash' of null, which does not describe the root cause of the issue and makes it difficult to debug.
If the current behavior is a bug, please provide the steps to reproduce.
What is the expected behavior?
An error message that describes the root cause, e.g.,
Undefined dependency "commonBAD" in "build/a.js"