Fixes error when there are no reports returned

Fixes

```
intel_client.py", line 62, in get_reports
    reports.extend(resp_json.get('resources', []))
TypeError: 'NoneType' object is not iterable
```

cs_misp_import/intel_client.py

@@ -59,7 +59,9 @@ def get_reports(self, start_time):
             offset += resp_json.get('meta', {}).get('pagination', {}).get('limit', 5000)
             first_run = False
 
-            reports.extend(resp_json.get('resources', []))
+            resources = resp_json.get('resources', [])
+            if resources is not None and len(resources) > 0:
+                reports.extend(resp_json.get('resources', []))
 
         return reports
 
@@ -149,4 +151,4 @@ def get_actor_name_list(self):
     def __check_metadata(resp_json):
         if (resp_json.get('meta', {}).get('pagination', {}).get('total') is None) \
                 or (resp_json.get('meta', {}).get('pagination', {}).get('limit') is None):
-            raise Exception(f'Unable to decode pagination metadata from response. Response is {resp_json}.')
+            raise Exception(f'Unable to decode pagination metadata from response. Response is {resp_json}.')