Fix copy_to(::Model, src) when src is nonlinear

[odow]

Closes #3100

[codecov]

Codecov Report

Base: 97.64% // Head: 97.63% // Decreases project coverage by -0.00% ⚠️

Coverage data is based on head (e39d64f) compared to base (2b2c321).
Patch coverage: 97.14% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3101      +/-   ##
==========================================
- Coverage   97.64%   97.63%   -0.01%     
==========================================
  Files          32       32              
  Lines        4328     4364      +36     
==========================================
+ Hits         4226     4261      +35     
- Misses        102      103       +1     

Impacted Files	Coverage Δ
src/copy.jl	96.15% <97.14%> (+0.43%)	⬆️
src/Containers/macro.jl	100.00% <0.00%> (ø)
src/Containers/container.jl	97.82% <0.00%> (+0.09%)	⬆️

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