问显示Eclipse中的错误，但程序正在运行

EN

1     '''
2     Created on Nov 19, 2013
3   
4     @author: martins
5     '''
6     bif = "background.jpg"
7     mif = "ball.png"
8   
9     import pygame, sys
10    from pygame.locals import *
11    
12    pygame.init()
13    screen = pygame.display.set_mode((800,800),0,32) #izveido logu
14    
15    background = pygame.image.load(bif).convert()#pārveido bildes
16    mouse_c = pygame.image.load(mif).convert_alpha()#pārveido bildes
17   
18    while True:
19        for event in pygame.event.get():
20            if event.type == QUIT:#nodrošina, ka programma pilnīgi aizveras
21              pygame.quit()
22                sys.exit()
23      
24      screen.blit(background,(0,0)) #nokopē backgroundu uz ekrāna(logā)
25      
26      x,y = pygame.mouse.get_pos()# noskaidro peles koardinātas
27      x-=mouse_c.get_width()/2 #ieliek kursoru bildei vid
28      y-=mouse_c.get_height()/2
29        
30      screen.blit(mouse_c,(x,y))#nokpē 
31       
32      pygame.display.update()