corrdata is still saved if not successfully split

[xtyangpsp]

In some case (not clear yet), the splitting may fail. It seems sometimes, the corrdata object that are not successfully split will still be saved. This needs to be fixed to avoid errors in later processing steps.

[xtyangpsp]

a thought is that when the data has less than 2 traces, the stacking would not do anything. this might lead to the skip of the splitting step. needs to check when I have a chance.