Sync additional test from jmespath.test

Author: jamesls

test/compliance/slice.json

@@ -131,7 +131,8 @@
   "given": {
     "foo": [{"a": 1}, {"a": 2}, {"a": 3}],
     "bar": [{"a": {"b": 1}}, {"a": {"b": 2}},
-	    {"a": {"b": 3}}]
+	    {"a": {"b": 3}}],
+    "baz": 50
   },
   "cases": [
     {
@@ -153,6 +154,10 @@
     {
       "expression": "bar[:2].a.b",
       "result": [1, 2]
+    },
+    {
+      "expression": "baz[:2].a",
+      "result": null
     }
   ]
 }, {