X Toolkit: Handle no tweets returned in search (#256)

## PR Description
Search ([see API docs
here](https://docs.x.com/x-api/posts/recent-search)) returns a 'data'
field that maps to a list of tweets returned. We've observed that the
'data' field is not present if no tweets match the search. This PR
handles that case safely.

toolkits/x/arcade_x/tools/tweets.py

@@ -94,7 +94,7 @@ async def search_recent_tweets_by_username(
 
     response_data: dict[str, Any] = response.json()
 
-    for tweet in response_data["data"]:
+    for tweet in response_data.get("data", []):
         expand_long_tweet(tweet)
 
     # Expand the URLs that are in the tweets
@@ -164,7 +164,7 @@ async def search_recent_tweets_by_keywords(
 
     response_data: dict[str, Any] = response.json()
 
-    for tweet in response_data["data"]:
+    for tweet in response_data.get("data", []):
         expand_long_tweet(tweet)
 
     # Expand the URLs that are in the tweets

toolkits/x/tests/test_tweets.py

@@ -141,6 +141,21 @@ async def test_search_recent_tweets_by_username_success(tool_context, mock_httpx
     mock_httpx_client.get.assert_called_once()
 
 
+@pytest.mark.asyncio
+async def test_search_recent_tweets_by_username_no_tweets_found(tool_context, mock_httpx_client):
+    """Test that the tool returns an empty list when no tweets are found."""
+    mock_response = MagicMock()
+    mock_response.status_code = 200
+    mock_response.json.return_value = {"next_token": ""}
+    mock_httpx_client.get.return_value = mock_response
+
+    username = "not_a_user_41"
+    result = await search_recent_tweets_by_username(tool_context, username)
+
+    assert "data" in result
+    assert len(result["data"]) == 0
+
+
 @pytest.mark.asyncio
 async def test_search_recent_tweets_by_username_failure(tool_context, mock_httpx_client):
     """Test failure when searching tweets due to API error."""
@@ -203,6 +218,21 @@ async def test_search_recent_tweets_by_keywords_success(tool_context, mock_httpx
     mock_httpx_client.get.assert_called_once()
 
 
+@pytest.mark.asyncio
+async def test_search_recent_tweets_by_keywords_no_tweets_found(tool_context, mock_httpx_client):
+    """Test that the tool returns an empty list when no tweets are found."""
+    mock_response = MagicMock()
+    mock_response.status_code = 200
+    mock_response.json.return_value = {"next_token": ""}
+    mock_httpx_client.get.return_value = mock_response
+
+    keywords = ["test", "keyword"]
+    result = await search_recent_tweets_by_keywords(context=tool_context, keywords=keywords)
+
+    assert "data" in result
+    assert len(result["data"]) == 0
+
+
 @pytest.mark.asyncio
 async def test_search_recent_tweets_by_keywords_no_input(tool_context):
     """Test error when no keywords or phrases are provided."""