fix(tools): search_files treats a JSON-null path like a blank one

The model can send `"path": null` as easily as `"path": ""`; on base a
None path reached search_tool and surfaced as an os.PathLike TypeError
instead of the documented current-directory default. Widen the blank-path
normalisation in _handle_search_files to any non-string and pin it in the
existing parametrized test.

Co-authored-by: joaomarcos <joaomarcosdias444@gmail.com>

tests/tools/test_search_files_engine_selection.py

@@ -288,8 +288,9 @@ def test_handler_forwards_modified_order(monkeypatch):
 
 
 @pytest.mark.parametrize("target", ["content", "files"])
-@pytest.mark.parametrize("blank_path", ["", " \t "])
+@pytest.mark.parametrize("blank_path", ["", " \t ", None])
 def test_handler_normalizes_blank_path_to_current_directory(monkeypatch, target, blank_path):
+    """#112424: a present-but-blank (or null) path must fall back to the documented '.' default."""
     captured = {}
 
     def fake_search_tool(**kwargs):

tools/file_tools.py

@@ -1291,8 +1291,10 @@ def _handle_search_files(args, **kw):
     target_map = {"grep": "content", "find": "files"}
     raw_target = args.get("target", "content")
     target = target_map.get(raw_target, raw_target)
+    # The schema documents path='.'; a present-but-blank (or JSON null) value
+    # is not a missing key for dict.get, so apply the default here (#112424).
     path = args.get("path", ".")
-    if isinstance(path, str) and not path.strip():
+    if not isinstance(path, str) or not path.strip():
         path = "."
     return search_tool(
         pattern=args.get("pattern", ""), target=target, path=path,