fix: ensure at least one worker is set based on CPU resources (#5510)

Signed-off-by: Frost Ming <[email protected]>

Author: frostming

src/_bentoml_sdk/service/factory.py

@@ -142,7 +142,7 @@ def __attrs_post_init__(self) -> None:
             from bentoml._internal.resource import system_resources
 
             resources = system_resources()
-            workers = min(16, int(resources["cpu"] / 2) + 1)
+            workers = min(16, int(resources["cpu"] / 2) or 1)
             self.config["workers"] = workers
 
     def __hash__(self):