Bug: if no V2 Libraries exist, calls to get_libraries are slow.

[connorhaugh]

Expected Behavior:
If an environment has no V2 libraries in existence, the studio view handler for Library Content Blocks,
https://studio/xblock/block_id/studio_view times out.
Here's the trace:

As a quick fix, I added a V2 lib to my site.
I then got this performance boost

t (an order of magnitude better)

This means that we need to make it so these calls:

edx-platform/xmodule/library_tools.py

Lines 193 to 195 in f2606ca

	v2_query = library_api.get_libraries_for_user(user)
	v2_libs_with_meta = library_api.get_metadata(v2_query)
	v2_libs = [(lib.key, lib.title) for lib in v2_libs_with_meta]

don't get sad and look for libraries that don't exist

specifically, I think the problem is blockstore's get get_bundles() method is called with None as input, which makes it sad.

[kdmccormick]

Need to confirm whether this is still true for Learning Core

[ormsbee]

Tested this locally, and it doesn't look like it's an issue with current implementation for Sumac.