Set file size to be "None"

This prevents a misleading file size of 0 bytes being displayed in
girder.

This is working without issues so far.

Signed-off-by: Patrick Avery <patrick.avery@kitware.com>

sources/dicom/large_image_source_dicom/assetstore/dicomweb_assetstore_adapter.py

@@ -356,7 +356,7 @@ def importData(self, parent, parentType, params, progress, user, **kwargs):
                     reuseExisting=True,
                     assetstore=self.assetstore,
                     mimeType='application/dicom',
-                    size=0,
+                    size=None,
                     saveFile=False,
                 )
                 file['dicom_uids'] = {