Bug in `IsColiftable` for `FinSets`

[lorenzo-lipparini]

Upon applying IsColiftable to certain morphisms in the category FinSets, CAP yields an error.
For comparison, analogous code on SkeletalFinSets does not produce an error and yields the expected result.

LoadPackage( "CAP", false );
LoadPackage( "FinSetsForCAP", false );


# With `SkeletalFinsets`, everything works fine

sone := FinSet( 1 );
stwo := FinSet( 2 );

sone_one := MapOfFinSets( sone, [ 1 ], sone );
sone_two := MapOfFinSets( sone, [ 1 ], stwo );

Display( IsColiftable( sone_one, sone_two ) );


# With `FinSets`, there is an unexpected error

one := FinSet( [ 1 ] );
two := FinSet( [ 1, 2 ] );

one_one := MapOfFinSets( one, [ [1,1] ], one );
one_two := MapOfFinSets( one, [ [1,1] ], two );

# All entities at play are well defined
Display( IsWellDefined( one ) );
Display( IsWellDefined( two ) );
Display( IsWellDefined( one_one ) );
Display( IsWellDefined( one_two ) );

# Error here
Display( IsColiftable( one_one, one_two ) );