[Maxima] bug with graphs::max_clique

[Oliver Kullmann]

Hi,

an error was introduced with 5.15 (while 5.14
worked correctly):

load(graphs);
max_clique(complete_graph(1));
max_degree: no max degree in an empty graph.

Obviously, the graph with one vertex has
a nice maximal clique (namely that vertex).
It seems to me that in general the graph-package
is somewhat sloppily written w.r.t. cases of "emptiness".

Oliver