Concurrent modification exception

[ronaldoeyeem]

stack trace from com.baseapp.eyeem

java.util.ConcurrentModificationException
       at java.util.HashMap$HashIterator.nextEntry(HashMap.java:806)
       at java.util.HashMap$ValueIterator.next(HashMap.java:838)
       at com.eyeem.storage.Storage.pushWithParams(Storage.java:234)
       at com.eyeem.storage.Storage.push(Storage.java:212)
       at com.baseapp.eyeem.storage.UserStorage.push(UserStorage.java:50)
       at com.baseapp.eyeem.tasks.FollowTask.sync(FollowTask.java:54)
       at com.baseapp.eyeem.tasks.FollowTask.onStart(FollowTask.java:35)
       at com.eyeem.mjolnir.PersistentTask.start(PersistentTask.java:43)
       at com.baseapp.eyeem.tasks.EyeEmTask.start(EyeEmTask.java:48)
       at com.baseapp.eyeem.fragment.UserListFragment$1.run(UserListFragment.java:322)
       at android.os.Handler.handleCallback(Handler.java:730)
       at android.os.Handler.dispatchMessage(Handler.java:92)
       at android.os.Looper.loop(Looper.java:176)
       at android.app.ActivityThread.main(ActivityThread.java:5419)
       at java.lang.reflect.Method.invokeNative(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:525)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862)
       at dalvik.system.NativeStart.main(NativeStart.java)