make process metadata saving more resilient

spiffworkflow-backend/src/spiffworkflow_backend/services/process_instance_processor.py

@@ -595,8 +595,13 @@ class ProcessInstanceProcessor:
             path_segments = path.split(".")
             data_for_key = current_data
             for path_segment in path_segments:
+                if path_segment in data_for_key:
                     data_for_key = data_for_key[path_segment]
+                else:
+                    data_for_key = None
+                    break
 
+            if data_for_key is not None:
                 pim = ProcessInstanceMetadataModel.query.filter_by(
                     process_instance_id=self.process_instance_model.id,
                     key=key,