JavaScript: can't edit files after installing AngularJS plugin

Check if the kotlin-runtime.jar exists in plugins/angularjs-plugin/lib (refer to Directories used by the IDE to store settings, caches, plugins and logs for the information about plugins location). if it's not there, remove the AngularJS plugin and reinstall it from the repository (Preferences/Plugins, Browse repositories...) - this should solve the problem.

Problems like this usually occur when installing plugin from disk if you extract the downloaded archive and select the angularjs-plugin.jar when installing instead of using the downloaded zip without unpacking it.