fix deadlock problem caused by recursion

[SKY123C]

import unreal
import threading

def a():
    print("a func")

def b():
    print("b func")
    unreal.executeInMainThreadWithResult(a)

def c():
    print("c func")
    unreal.executeInMainThreadWithResult(b)
    
my_thread = threading.Thread(target=c)
my_thread.start()

this commit can fix this program