Fix post `v0.11.0` bugs - 500 error on missing local collection, 400 error from proxied v2 paginated requests

[briantist]

Fixes #112 Fixes #113

[codecov[bot]]

Codecov Report

Attention: 11 lines in your changes are missing coverage. Please review.

Comparison is base (41fd9b0) 62.60% compared to head (d476a4d) 62.52%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #114 +/- ## ========================================== - Coverage 62.60% 62.52% -0.09% ========================================== Files 33 33 Lines 1511 1513 +2 ========================================== Hits 946 946 - Misses 565 567 +2 ``` | [Files](https://app.codecov.io/gh/briantist/galactory/pull/114?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Brian+Scholer) | Coverage Δ | | |---|---|---| | [galactory/upstream.py](https://app.codecov.io/gh/briantist/galactory/pull/114?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Brian+Scholer#diff-Z2FsYWN0b3J5L3Vwc3RyZWFtLnB5) | `21.98% <0.00%> (-0.24%)` | :arrow_down: | | [galactory/api/v2/collections.py](https://app.codecov.io/gh/briantist/galactory/pull/114?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Brian+Scholer#diff-Z2FsYWN0b3J5L2FwaS92Mi9jb2xsZWN0aW9ucy5weQ==) | `18.48% <0.00%> (ø)` | | | [galactory/api/v3/collections.py](https://app.codecov.io/gh/briantist/galactory/pull/114?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Brian+Scholer#diff-Z2FsYWN0b3J5L2FwaS92My9jb2xsZWN0aW9ucy5weQ==) | `23.25% <0.00%> (ø)` | |

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