fix: skip search_web citations if tool result is not a list

Author: Algorithm5838

backend/open_webui/utils/middleware.py

@@ -194,6 +194,8 @@ def get_citation_source_from_tool_result(
         if tool_name == "search_web":
             # Parse JSON array: [{"title": "...", "link": "...", "snippet": "..."}]
             results = tool_result
+            if not isinstance(results, list):
+                return []
             documents = []
             metadata = []