fix: shared MCP truncate() crashes on None/non-string tool output (#1605)

mcp_servers/_common.py

@@ -13,6 +13,10 @@ SEARCH_TIMEOUT = 30
 
 def truncate(text: str, limit: int = MAX_OUTPUT_CHARS) -> str:
     """Truncate text to *limit* characters with a suffix note."""
+    if not isinstance(text, str):
+        # Tool output is occasionally None or a non-string; len(None) would
+        # raise. Coerce so this shared helper never crashes a tool response.
+        text = "" if text is None else str(text)
     if len(text) > limit:
         return text[:limit] + f"\n... (truncated, {len(text)} chars total)"
     return text