[Fix] Stackoverflow in BlockSparseArray constructor with wrong number of axes

[lkdvos]

Fixes #108

using BlockSparseArrays
a = BlockSparseArray{Float64,2,Matrix{Float64}}(undef, ([2, 2], [2, 2])) # works
a = BlockSparseArray{Float64,2,Matrix{Float64}}(undef, ([2, 2],)) # should error - instead hangs indefinitely

By explicitly checking the length and throwing an error.
The alternative would be to simply restrict that constructor to only take length N tuples, which would throw a MethodError instead.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.07%. Comparing base (3ba5eca) to head (f64112b).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #109      +/-   ##
==========================================
+ Coverage   75.04%   75.07%   +0.02%     
==========================================
  Files          27       27              
  Lines        1062     1063       +1     
==========================================
+ Hits          797      798       +1     
  Misses        265      265              

Flag	Coverage Δ
docs	16.63% <0.00%> (-0.02%)	⬇️

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[mtfishman]

Thanks!