fix(overmind): check actual plain object when processing state

Author: christianalfoni

packages/node_modules/overmind/src/index.ts

@@ -10,14 +10,9 @@ import ActionClass, {
 } from './Action'
 import Derived from './derived'
 import Devtools, { Message, safeValue } from './Devtools'
-import {
-  DynamicModule,
-  EventType,
-  Events,
-  Options,
-  SubType,
-} from './internalTypes'
+import { DynamicModule, EventType, Events, Options } from './internalTypes'
 import Reaction from './reaction'
+const isPlainObject = require('is-plain-object')
 
 export { modules } from './modules'
 
@@ -387,7 +382,7 @@ export default class App<
   private processState(state: {}) {
     return Object.keys(state).reduce((aggr, key) => {
       const value = state[key]
-      if (typeof value === 'object') {
+      if (isPlainObject(value)) {
         aggr[key] = this.processState(value)
       } else if (typeof value === 'function') {
         aggr[key] = new Derived(value)