Remove plugin fallback to root options/defaults

Author: kurkle

docs/docs/general/options.md

@@ -60,11 +60,9 @@ Each scope is looked up with `elementType` prefix in the option name first, then
 * options.plugins[`plugin.id`]
 * options.controllers[`config.type`].plugins[`plugin.id`]
 * (options.[`...plugin.additionalOptionScopes`])
-* options
 * defaults.controllers[`config.type`].plugins[`plugin.id`]
 * defaults.plugins[`plugin.id`]
 * (defaults.[`...plugin.additionalOptionScopes`])
-* defaults
 
 ## Scriptable Options
 

src/core/core.plugins.js

@@ -168,8 +168,7 @@ function pluginOpts(config, plugin, opts, context) {
   const keys = [
     `controllers.${config.type}.plugins.${id}`,
     `plugins.${id}`,
-    ...plugin.additionalOptionScopes || [],
-    ''
+    ...plugin.additionalOptionScopes || []
   ];
   const scopes = config.getOptionScopes(opts || {}, keys);
   return config.createResolver(scopes, context);