fix bug

main.py

@@ -131,8 +131,9 @@ def getThumbnails(imgs):
     thumbs = []
     thumb_size = (256, 256)
     for img in imgs:
-        img.thumbnail(thumb_size)
-        thumbs.append(img)
+        th = img.copy()
+        th.thumbnail(thumb_size)
+        thumbs.append(th)
     return thumbs