Some fixes on empty digraphs

Author: ap4108735

tst/standard/weights.tst

@@ -109,17 +109,17 @@ Error, the argument <D> must be a connected digraph,
 
 # digraph with one node
 gap> d := EdgeWeightedDigraph([[]], [[]]);
-<immutable edge-weighted empty digraph with 1 vertex>
+<immutable empty digraph with 1 vertex>
 gap> tree := EdgeWeightedDigraphMinimumSpanningTree(d);
-<immutable edge-weighted empty digraph with 1 vertex>
+<immutable empty digraph with 1 vertex>
 gap> EdgeWeightedDigraphTotalWeight(tree);
 0
 
 # digraph with loop
 gap> d := EdgeWeightedDigraph([[1]], [[5]]);
 <immutable edge-weighted digraph with 1 vertex, 1 edge>
 gap> EdgeWeightedDigraphMinimumSpanningTree(d);
-<immutable edge-weighted empty digraph with 1 vertex>
+<immutable empty digraph with 1 vertex>
 
 # digraph with cycle
 gap> d := EdgeWeightedDigraph([[2], [3], [1]], [[5], [10], [15]]);
@@ -153,7 +153,7 @@ gap> EdgeWeightedDigraphMinimumSpanningTree(d);
 
 # Shortest paths: one node
 gap> d := EdgeWeightedDigraph([[]], [[]]);
-<immutable edge-weighted empty digraph with 1 vertex>
+<immutable empty digraph with 1 vertex>
 gap> EdgeWeightedDigraphShortestPaths(d, 1);
 rec( distances := [ 0 ], edges := [ fail ], parents := [ fail ] )