Refactor jump_search to check for empty array first

Author: cclauss

searches/jump_search.py

@@ -36,10 +36,9 @@ def jump_search[T: Comparable](arr: Sequence[T], item: T) -> int:
     >>> jump_search([], 1)
     -1
     """
-
-    arr_size = len(arr)
-    if arr_size == 0:
+    if not arr:
         return -1
+    arr_size = len(arr)
 
     block_size = int(math.sqrt(arr_size))