Fix LongGen accidentally using special cases when none are desired

Signed-off-by: Jason Lowe <[email protected]>

integration_tests/src/main/python/data_gen.py

@@ -280,10 +280,13 @@ def random_decimal(rand):
 
 LONG_MIN = -(1 << 63)
 LONG_MAX = (1 << 63) - 1
+_MISSING_ARG = object()
+
 class LongGen(DataGen):
     """Generate Longs, which some built in corner cases."""
-    def __init__(self, nullable=True, min_val = LONG_MIN, max_val = LONG_MAX, special_cases = []):
-        _special_cases = [min_val, max_val, 0, 1, -1] if not special_cases else special_cases
+    def __init__(self, nullable=True, min_val = LONG_MIN, max_val = LONG_MAX,
+                 special_cases = _MISSING_ARG):
+        _special_cases = [min_val, max_val, 0, 1, -1] if special_cases is _MISSING_ARG else special_cases
         super().__init__(LongType(), nullable=nullable, special_cases=_special_cases)
         self._min_val = min_val
         self._max_val = max_val