fix: don't allow undefined values to override defaults

[danielroe]

closes #273

[codecov-commenter]

Codecov Report

Merging #274 (e5f34e0) into main (7e06ea6) will decrease coverage by 42.51%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##             main     #274       +/-   ##
===========================================
- Coverage   56.47%   13.96%   -42.52%     
===========================================
  Files          22       20        -2     
  Lines         517      451       -66     
  Branches      129      115       -14     
===========================================
- Hits          292       63      -229     
- Misses        225      388      +163     

Impacted Files	Coverage Δ
src/runtime/image.ts	0.00% <0.00%> (-68.87%)	⬇️
src/runtime/providers/cloudinary.ts	0.00% <0.00%> (-80.96%)	⬇️
src/runtime/providers/imgix.ts	0.00% <0.00%> (-100.00%)	⬇️
src/runtime/providers/fastly.ts	0.00% <0.00%> (-100.00%)	⬇️
src/runtime/providers/static.ts	0.00% <0.00%> (-100.00%)	⬇️
src/runtime/providers/ipx.ts	0.00% <0.00%> (-84.62%)	⬇️
src/runtime/components/image.mixin.ts	0.00% <0.00%> (-81.82%)	⬇️
src/runtime/providers/twicpics.ts	0.00% <0.00%> (-72.23%)	⬇️
src/runtime/providers/imagekit.ts	0.00% <0.00%> (-63.64%)	⬇️
... and 6 more

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