Make ophys analysis functions robust to lack of events table

[matchings]

Sometimes event detection fails, resulting in the events table in the SDK output being empty. The lack of events causes some functions that expect it to fail, including build_tidy_cell_df.

We need to add some exceptions or modifications to the code such that it works without events, and/or is flexible to the type of traces that are used, such as asking users to provide string values of which types they want - dff, events, filtered events, perhaps even corrected_fluorescence.