Avoid warning about empty Series

diff between pandas 1 and 2. but we can actually just return the result if its empty

Author: FlorentinD

graphdatascience/model/model.py

@@ -201,7 +201,7 @@ def drop(self, failIfMissing: bool = False) -> Series[Any]:
             ).squeeze()
 
             if result.empty:
-                return Series()
+                return result
 
             #  modelInfo {.*, modelName: modelName, modelType: modelType} AS modelInfo
             result["modelInfo"] = {