Allow an empty list of matrices in RightModuleOverPathAlgebra.

[erich-9]

If possible, I would like to be allowed to create the zero module with the following command:

RightModuleOverPathAlgebra(A, []);

This doesn't work at the moment since GAP Collections cannot be empty. With the changes in this commit the command above will work. But maybe there is a better way to implement it.

[codecov[bot]]

Codecov Report

Merging #41 into master will increase coverage by <.01%. The diff coverage is 85.71%.

@@            Coverage Diff             @@
##           master      #41      +/-   ##
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+ Coverage   59.71%   59.72%   +<.01%     
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  Files          70       70              
  Lines       20455    20462       +7     
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+ Hits        12214    12220       +6     
- Misses       8241     8242       +1

Impacted Files	Coverage Δ
lib/module.gd	100% <100%> (ø)	:arrow_up:
lib/module.gi	66.27% <83.33%> (+0.07%)	:arrow_up:

[sunnyquiver]

The zero module over a path algebra can be constructed via

gap> ZeroModule(A);                            
<[ 0, 0, 0 ]>

or via

gap> RightModuleOverPathAlgebra(A, [0,0,0],[]);
<[ 0, 0, 0 ]>

Is this sufficient?

[erich-9]

Yes, this is sufficient. Thank you.

After thinking about it again, it is probably not even a good idea if the command above returned the zero module (even if it might me convenient in some places).