fix: Allow arbitrary reshape in projection if array is zero sized

[lenianiva]

This fixes a bug where during backpropagation the size of an array e.g. (1, 1, 0) does not match the size of the gradient e.g. (4, 1, 0). The error only happens for zero-sized arrays.

See an example here: JuliaGraphs/GraphNeuralNetworks.jl#638

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.50%. Comparing base (004e43e) to head (8a5c3e9).

Additional details and impacted files

@@ Coverage Diff @@## main #702 +/- ##
=======================================
Coverage 93.49% 93.50% =======================================
Files 15 15 Lines 999 1000 +1 =======================================
+ Hits 934 935 +1 
Misses 65 65 

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[CarloLucibello]

merge?

[devmotion]

It would be interesting to know first why the gradient has an incorrect shape. And ideally then we could fix the underlying issue instead of relaxing the projection.