Not process gaps when gap minimum is set empty in GUI

sohstationviewer/model/general_data/general_data.py

@@ -370,6 +370,8 @@ class GeneralData():
         """
         for data_set_id in self.data_set_ids:
             self.gaps[data_set_id] = []
+            if self.gap_minimum is None:
+                continue
             retrieve_gaps_from_data_dict(data_set_id,
                                          self.soh_data, self.gaps)
             retrieve_gaps_from_data_dict(data_set_id,