fix bad filter testcase 2

Author: ElijahSwiftIBM

python/cbxp/cbxp.py

@@ -73,6 +73,6 @@ def cbxp(
     )
     if response["return_code"]:
         raise CBXPError(response["return_code"], control_block)
-    if response["result_json"] == {} and filter_key != "":
+    if response["result_json"] == "null" and filter_key != "":
         raise CBXPError(CBXPErrorCode.NO_FILTER_MATCH.value, control_block)
     return json.loads(response["result_json"])

tests/test.py

@@ -267,7 +267,8 @@ def test_cbxp_raises_cbxp_error_if_filter_uses_non_included_control_block(
     ):
         with self.assertRaises(CBXPError) as e:
             cbxp(
-                "psa", control_block_filter={"cvt.asvt.ascb.assb.assbjbni": "MASTER  "}
+                "psa",
+                control_block_filter={"cvt.asvt.ascb.assb.assbjbni": "MASTER  "},
             )
         self.assertEqual("A bad filter was provided", str(e.exception))