fix: check that frozen.build exists before trying to access it

If there is a compilation where frozen.build is not generated for some reason,
then the check here would fail and throw an exception:

   Could not freeze FILE_NAME: Cannot read property 'hash' of undefined

We check to see if the build exists and then fall through to regenerate if
it does not.

Author: Conor Hunt

lib/TransformNormalModulePlugin.js

@@ -598,7 +598,7 @@ class TransformNormalModulePlugin {
           module.request &&
           (cacheable(module) || !module.built) &&
           module instanceof NormalModule &&
-          (!frozen ||
+          (!frozen || !frozen.build ||
             (schema >= 4 && module.hash !== frozen.build.hash) ||
             (schema < 4 &&
               module.getHashDigest(extra.compilation.dependencyTemplates) !==