semirel: add family check to GreensXClassOfElement

This commit adds a check that the family of the object and the elements
family of the family of the semigroup passed to the methods
GreensXClassOfElement, where X in [R, L, H, D, J], are equal. This
prevents the creation of Green's classes with wholly the wrong type of
objects as representatives.

lib/semirel.gi

@@ -250,33 +250,38 @@ end);
 #O  GreensHClassOfElement(<semigroup>, <representative>)
 ##
 
-InstallMethod(GreensRClassOfElement, "for a semigroup and object",
-[IsSemigroup and HasIsFinite and IsFinite, IsObject],
+InstallMethod(GreensRClassOfElement, "for a semigroup and object", 
+IsCollsElms,
+[IsSemigroup and HasIsFinite and IsFinite, IsObject], 
 function(s,e)
   return EquivalenceClassOfElementNC( GreensRRelation(s), e );
 end);
 
 InstallMethod(GreensLClassOfElement, "for a semigroup and object",
+IsCollsElms,
 [IsSemigroup and HasIsFinite and IsFinite, IsObject],
 function(s,e)
   return EquivalenceClassOfElementNC( GreensLRelation(s), e );
 end);
 
 
 InstallMethod(GreensHClassOfElement, "for a semigroup and object",
+IsCollsElms,
 [IsSemigroup and HasIsFinite and IsFinite, IsObject],
 function(s,e)
   return EquivalenceClassOfElementNC( GreensHRelation(s), e );
 end);
 
 
 InstallMethod(GreensDClassOfElement, "for a semigroup and object", 
+IsCollsElms,
 [IsSemigroup and HasIsFinite and IsFinite, IsObject],
 function(s,e)
   return EquivalenceClassOfElementNC( GreensDRelation(s), e );
 end);
 
 InstallMethod(GreensJClassOfElement, "for a semigroup and object", 
+IsCollsElms,
 [IsSemigroup and HasIsFinite and IsFinite, IsObject],
 function(s,e)
   return EquivalenceClassOfElementNC( GreensJRelation(s), e );