make sure inbound sms page doesn't break if you receive a blank inbound message

app/main/views/conversation.py

@@ -73,7 +73,10 @@ def get_sms_thread(service_id, user_number):
             'inbound': is_inbound,
             'content': SMSPreviewTemplate(
                 {
-                    'content': notification.get('content') or notification['template']['content']
+                    'content': (
+                        notification['content'] if is_inbound else
+                        notification['template']['content']
+                    )
                 },
                 notification.get('personalisation'),
                 downgrade_non_gsm_characters=(not is_inbound),

tests/app/main/views/test_conversation.py

@@ -1,19 +1,19 @@
+from datetime import datetime
 import json
 import pytest
-from bs4 import BeautifulSoup
 
+from bs4 import BeautifulSoup
 from flask import (
     url_for,
 )
 from notifications_python_client.errors import HTTPError
+from freezegun import freeze_time
+
 from tests.conftest import (
     SERVICE_ONE_ID,
     normalize_spaces,
     mock_get_notifications,
-    mock_get_inbound_sms,
 )
-from freezegun import freeze_time
-from unittest import mock
 from app.main.views.conversation import get_user_number
 
 
@@ -78,6 +78,7 @@ def test_view_conversation(
     fake_uuid,
     outbound_redacted,
     expected_outbound_content,
+    mock_get_inbound_sms
 ):
 
     mock_get_notifications(
@@ -88,10 +89,6 @@ def test_view_conversation(
         redact_personalisation=outbound_redacted,
     )
 
-    mock_get_inbound_sms(
-        mocker
-    )
-
     page = client_request.get(
         'main.conversation',
         service_id=SERVICE_ONE_ID,
@@ -186,3 +183,32 @@ def test_view_conversation_updates(
     assert json.loads(response.get_data(as_text=True)) == {'messages': 'foo'}
 
     mock_get_partials.assert_called_once_with(SERVICE_ONE_ID, '07123 456789')
+
+
+@freeze_time("2012-01-01 00:00:00")
+def test_view_conversation_with_empty_inbound(
+    client_request,
+    mocker,
+    api_user_active,
+    mock_get_notification,
+    mock_get_notifications_with_no_notifications,
+    fake_uuid
+):
+    mock_get_inbound_sms = mocker.patch(
+        'app.main.views.conversation.service_api_client.get_inbound_sms',
+        return_value=[{
+            'user_number': '07900000001',
+            'content': '',
+            'created_at': datetime.utcnow().isoformat(),
+            'id': fake_uuid
+        }]
+    )
+
+    page = client_request.get(
+        'main.conversation',
+        service_id=SERVICE_ONE_ID,
+        notification_id=fake_uuid,
+    )
+
+    messages = page.select('.sms-message-wrapper')
+    assert len(messages) == 1