Fix no_diff with missing pre and post snapfile

lib/jnpr/jsnapy/operator.py

@@ -559,8 +559,8 @@ def not_exists(
                         count_pass = count_pass + 1
                         node_value_passed = {
                             "id": id_val,
-                            "PRE": predict,
-                            "POST": postdict,
+                            "pre": predict,
+                            "post": postdict,
                             "message": message,
                         }
                         tresult["passed"].append(deepcopy(node_value_passed))
@@ -2739,6 +2739,18 @@ def no_diff(
                 + "ERROR!! 'no-diff' operator requires node value to test !!",
                 extra=self.log_detail,
             )
+        elif xml1 is None or xml2 is None:
+            self._error_nodes_logger("Xpath for snapshot", x_path)
+            res = False
+            count_fail = count_fail + 1
+            node_value_failed = {
+                "id": iddict,
+                "pre": predict,
+                "post": postdict,
+                "actual_node_value": None,
+                "xpath_error": True,
+            }
+            tresult["failed"].append(deepcopy(node_value_failed))
         else:
             if (not pre_nodes) or (not post_nodes):
                 # if ignore_null is True, just skip
@@ -2873,7 +2885,8 @@ def no_diff(
                     else:
                         # mapping id name to its value
                         for length in range(len(k)):
-                            id_val[id_list[length]] = k[length][0].strip()
+                            if len(k[0]) > 0:
+                                id_val[id_list[length]] = k[length][0].strip()
                         if k in data1:
                             predict, postdict = self._get_nodevalue(
                                 predict,