fix(tracker): drop functions and methods from state in mobx

tracker/tracker-mobx/package.json

@@ -1,7 +1,7 @@
 {
   "name": "@openreplay/tracker-mobx",
   "description": "Tracker plugin for MobX events recording",
-  "version": "4.0.1",
+  "version": "4.0.2",
   "keywords": [
     "mobx",
     "logging",

tracker/tracker-mobx/src/log.ts

@@ -61,8 +61,14 @@ const compute = ev => {
 
 
 const observeAction = ev => {
+  const state = {}
+  for (let property in ev.object) {
+    if (typeof property !== 'function') {
+      state[property] = ev.object[property]
+    }
+  }
   return {
-    state: ev.object,
+    state,
     type: ev.type,
     property: ev.name,
   }