Version

3.0.0

Node and OS info

yarn 1.9.4 / Linux Mint 19

Steps to reproduce

Just typing vue inspect --rule vue OR vue inspect --rules shows this error.

What is expected?

A list of webpack rules.

What is actually happening?

TypeError: Cannot read property '0' of undefined
at config.module.rules.map.r (/home/jesus/apps/annexum-new-webpack/node_modules/@vue/cli-service/lib/commands/inspect.js:25:55)
at Array.map ()
at api.registerCommand.args (/home/jesus/apps/annexum-new-webpack/node_modules/@vue/cli-service/lib/commands/inspect.js:25:33)
at Service.run (/home/jesus/apps/annexum-new-webpack/node_modules/@vue/cli-service/lib/Service.js:203:12)
at Object. (/home/jesus/apps/annexum-new-webpack/node_modules/@vue/cli-service/bin/vue-cli-service.js:22:9)
at Module._compile (module.js:649:30)
at Object.Module._extensions..js (module.js:660:10)
at Module.load (module.js:561:32)
at tryModuleLoad (module.js:501:12)
at Function.Module._load (module.js:493:3)
at Function.Module.runMain (module.js:690:10)
at startup (bootstrap_node.js:194:16)
at bootstrap_node.js:666:3