Some small fixes and improvements

[pkgw]

Fixing a new test error, some test warnings, and some issues spotted when trying to toast Nico Carver's large RGB image.

[codecov[bot]]

Codecov Report

Attention: 16 lines in your changes are missing coverage. Please review.

Comparison is base (3f0c5e0) 73.55% compared to head (2eb6d99) 73.29%.

Files	Patch %	Lines
toasty/cli.py	0.00%	15 Missing :warning:
toasty/samplers.py	50.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #99 +/- ## ========================================== - Coverage 73.55% 73.29% -0.26% ========================================== Files 24 24 Lines 3971 3985 +14 ========================================== Hits 2921 2921 - Misses 1050 1064 +14 ```

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