[Data] Fix validation bug when size=0 in ActorPoolStrategy (ray-proje…

…ct#47072)

To resolve the issue 40393 and we need to check if size is not None beforehand.

Signed-off-by: Xingyu Long <halolong@hotmail.com>

python/ray/data/_internal/compute.py

@@ -88,7 +88,7 @@ def __init__(
                 computation and avoiding actor startup delays, but will also increase
                 queueing delay.
         """
-        if size:
+        if size is not None:
             if size < 1:
                 raise ValueError("size must be >= 1", size)
             if max_size is not None or min_size is not None: