Misleading warning emitted when saving movie without file_name to hdf5 (e.g. doing motion correction without saving first)

[ethanbb]

Your setup:

1. Operating System (Linux, MacOS, Windows): Linux
2. Hardware type (x86, ARM..) and RAM: x86, 128 GB
3. Python Version (e.g. 3.9): 3.11
4. Caiman version (e.g. 1.9.12): 1.11.3
5. Which demo exhibits the problem (if applicable): N/A
6. How you installed Caiman (pure conda, conda + compile, colab, ..): conda + compile
7. Details:

I encountered the "No file saved" warning when trying to do motion correction on just an ndarray (for a test). There is code to save an ndarray or movie to a temporary .hdf5 file first, but it doesn't set the file_name attribute on the movie if it's not already a movie that has one. As a result, saving file_name fails:

CaImAn/caiman/base/timeseries.py

Lines 297 to 300 in bb55800

	try:
	dset.attrs["file_name"] = [a.encode('utf8') for a in self.file_name]
	except:
	logger.warning('No file saved')

...because file_name is [None] and (None).encode('utf8') doesn't work. In practice, I realized since it's just a warning the code will continue and work as expected, but may as well fix it to avoid any doubt.

Suggested fix: change to dset.attrs["file_name"] = [a.encode('utf8') for a in self.file_name if a is not None]
Optional additional fix: in motion_correction.py line 177, set file_name when creating the movie: caiman.movie(fname, file_name=mc_tempfile).save(mc_tempfile) (however this will not overwrite file_name if fname is already a movie)

[pgunn]

Longer term we'll probably not want to base filenames on each other as we improve pathing logic and keep runs isolated from each other while saving metadata elsewhere (likely instead just using a static filename), but this seems like a good solution in the middle term.