TMSS-320: use defaults

SAS/TMSS/src/tmss/tmssapp/adapters/sip.py

@@ -185,8 +185,8 @@ def create_sip_representation_for_subtask(subtask: Subtask):
             pipeline = siplib.AveragingPipeline(  # <-- this is what we need for UC1
                 pipeline_map,
                 numberofcorrelateddataproducts=get_number_of_dataproducts_of_type(subtask, Dataformat.Choices.MEASUREMENTSET.value),
-                frequencyintegrationstep=subtask.specifications_doc['demixer']['frequency_steps'] if 'demix' in subtask.task_blueprint.specifications_doc else 0,
-                timeintegrationstep=subtask.specifications_doc['demixer']['time_step'] if 'demix' in subtask.task_blueprint.specifications_doc else 0,
+                frequencyintegrationstep=subtask.specifications_doc.get('demixer',{}).get('frequency_steps', 0),
+                timeintegrationstep=subtask.specifications_doc.get('demixer',{}).get('time_step', 0),
                 flagautocorrelations=subtask.task_blueprint.specifications_doc["flag"]["autocorrelations"],
                 demixing=True if 'demix' in subtask.task_blueprint.specifications_doc else False
             )