Fix old sparsity representation

src/spikeinterface/core/waveform_extractor.py

@@ -1928,11 +1928,17 @@ def load(cls, folder, waveform_extractor):
             params = cls.load_params_from_folder(folder)
 
         if "sparsity" in params and params["sparsity"] is not None:
+            sparsity_params = params["sparsity"]
+            # handle old sparsity version
+            if "unit_ids" not in params["sparsity"]:
+                sparsity_params = {}
+                sparsity_params["unit_ids"] = waveform_extractor.unit_ids
+                sparsity_params["channel_ids"] = waveform_extractor.channel_ids
+                sparsity_params["unit_id_to_channel_ids"] = params["sparsity"]
+            else:
+                sparsity_params = params["sparsity"]
             params["sparsity"] = ChannelSparsity.from_dict(params["sparsity"])
 
-        # if waveform_extractor is None:
-        #     waveform_extractor = WaveformExtractor.load(folder)
-
         # make instance with params
         ext = cls(waveform_extractor)
         ext._params = params